Swift: To struct, or not to struct

I'm finally making the switch from Objective-C to Swift. I'm creating a view layout system for my client to make their apps more flexible in layout, without using auto layout as they want to design their screens remotely and auto-layout would be too complex for them. I tried to do this using structs and protocols but I found it to be quite clumsy, so I'm suspecting I'm not thinking about it the right way.

With classes, the structure would be as follows:

class ViewModel {
    var frame: CGRect = .zero
}

class ViewGroupModel: ViewModel {
    var weight: Int = 1
    var children:[ViewModel] = [ViewModel]()
}

class HorizontalViewGroupModel: ViewGroupModel {
}

class VerticalViewGroupModel: ViewGroupModel {
}

I tried to approach it with protocols by defining a ViewModel protocol, and a ViewGroupModel protocol, but I found it created a lot of duplication (properties). Is there a better approach? Would it be considered a good practice to use classes in this case?

EDIT: In case it would be better to not uses classes, I am looking for an answer that gives me a concrete solution in terms of structs and protocols.