一つのViewController上に２つのpageViewControllerを表示することは可能でしょうか？

一つのViewController上に2つのPageViewControllerを設置したいのですが、
setPageViewController()/setViewControllers(_:direction:animated:completion:)で設置するPageViewControllerを選ぶことができません(適当な方へ設置される)。
どちらか指定する方法をご存知でしたら教えて下さい。
tableViewなどではOutlet接続して名前をつけることによって指定できますが、pageViewControllerの名前の付け方がわかりませんでした。

サンプル

↓このような感じのコードで設置しようとしています。

swift
1import UIKit
2
3class ViewController: UIViewController {
4    
5    var upperPageViewController: UIPageViewController!
6    var lowerPageViewController: UIPageViewController!
7    
8    var upperPageViewArray: [String] = ["A", "B", "C", "D", "E"]
9    var lowerPageViewArray: [String] = ["あ", "か", "さ", "た", "な"]
10    
11    var upperPageViewIndex: Int = 0
12    var lowerPageViewIndex: Int = 0
13    
14    override func viewDidLoad() {
15        super.viewDidLoad()
16        // pageViewControllerの設定 -> prepareへ
17        // pageControlの設定
18        setUpperPageViewController()
19        setLowerPageViewController()
20
21        upperPageViewController?.delegate   = self
22        upperPageViewController?.dataSource = self
23        lowerPageViewController?.delegate   = self
24        lowerPageViewController?.dataSource = self
25    }
26    
27    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
28        switch segue.identifier {
29        case "EmbedUpperPVC":
30            upperPageViewController = (segue.destination as! UIPageViewController)
31        case "EmbedLowerPVC":
32            lowerPageViewController = (segue.destination as! UIPageViewController)
33        default: fatalError("prepare")
34        }
35    }
36    
37}
38
39
40
41extension ViewController: UIPageViewControllerDelegate {
42    
43    func pageViewController(_ pageViewController: UIPageViewController,
44                            didFinishAnimating finished: Bool,
45                            previousViewControllers: [UIViewController],
46                            transitionCompleted completed: Bool)
47    {
48         
49        if completed {
50           switch pageViewController {
51            case upperPageViewController:
52                guard let vc = upperPageViewController?.viewControllers?.first as? ContentsVC else { return }
53                let index = vc.dataSource.index
54                self.upperPageViewIndex = index
55            case lowerPageViewController:
56                guard let vc = lowerPageViewController?.viewControllers?.first as? ContentsVC else { return }
57                let index = vc.dataSource.index
58                self.lowerPageViewIndex = index
59                default: fatalError("pageViewController/didFinishAnimating/fatalError")
60            }
61        }
62    }
63}
64
65extension ViewController: UIPageViewControllerDataSource {
66    
67    func pageViewController(_ pageViewController: UIPageViewController,
68                            viewControllerBefore viewController: UIViewController) -> UIViewController?
69    {
70        var index: Int
71        let str: String
72        
73        switch pageViewController {
74        case upperPageViewController:
75            index = upperPageViewIndex
76            if index == 0 { return nil }
77            index -= 1
78            str = upperPageViewArray[index]
79        case lowerPageViewController:
80            index = lowerPageViewIndex
81            if index == 0 { return nil }
82            index -= 1
83            str = lowerPageViewArray[index]
84        default: fatalError("viewControllerBefore/fatalError")
85        }
86        guard let vc = createContentsVC(index: index, str: str) else { return nil }
87        
88        return vc
89    }
90    
91    func pageViewController(_ pageViewController: UIPageViewController,
92                            viewControllerAfter viewController: UIViewController) -> UIViewController?
93    {
94        var index: Int
95        let str: String
96        
97        switch pageViewController {
98        case upperPageViewController:
99            index = upperPageViewIndex
100            if index >= upperPageViewArray.count - 1 { return nil }
101            index += 1
102            str = upperPageViewArray[index]
103        case lowerPageViewController:
104            index = lowerPageViewIndex
105            if index >= lowerPageViewArray.count - 1 { return nil }
106            index += 1
107            str = lowerPageViewArray[index]
108        default: fatalError("viewControllerBefore/fatalError")
109        }
110        guard let vc = createContentsVC(index: index, str: str) else { return nil }
111        
112        return vc
113    }
114    
115}
116
117// setPageViewController
118extension ViewController {
119    
120    func setUpperPageViewController(direction: UIPageViewController.NavigationDirection = .forward) {
121        
122        let index = upperPageViewIndex
123        let str   = upperPageViewArray[index]
124        
125        guard let vc = createContentsVC(index: index, str: str) else { return }
126       
127        self.upperPageViewController?.setViewControllers([vc], direction: .forward, animated: false, completion: nil)
128    }
129    
130    func setLowerPageViewController(direction: UIPageViewController.NavigationDirection = .forward) {
131        
132        let index = lowerPageViewIndex
133        let str   = lowerPageViewArray[index]
134        
135        guard let vc = createContentsVC(index: index, str: str) else { return }
136        
137        self.lowerPageViewController?.setViewControllers([vc], direction: .forward, animated: false, completion: nil)
138    }
139    
140    func createContentsVC(index: Int, str: String) -> UIViewController? {
141        
142        let sb = UIStoryboard(name: "Main", bundle: nil)
143        let vc = sb.instantiateViewController(withIdentifier: "ContentsVC") as! ContentsVC
144        vc.dataSource = ContentsVCDataStore.init(index: index, str: str)
145        
146        return vc
147    }
148    
149}
150
151
152class ContentsVC: UIViewController {
153    
154    var dataSource: ContentsVCDataStore!
155    
156    @IBOutlet weak var tLabel: UILabel!
157    
158    override func viewDidLoad() {
159        super.viewDidLoad()
160        tLabel.text = dataSource.str
161    }
162}
163
164class ContentsVCDataStore {
165    
166    var index: Int
167    var str: String
168    
169    init(index: Int, str: String) {
170        self.index = index
171        self.str = str
172    }
173}
174