Generic List ModelBinding

Controllers\HomeController.cs

    using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Diagnostics;

namespace AjaxMvcTest.Controllers {
    public class HomeController : Controller {
        //
        // GET: /Home/

        
        public ActionResult Index() {
            HomeModel model = new HomeModel();
            model.Header = "Default Header";
            model.Content = "People assume that time is a strict progression of cause to effect, but actually, from a non-linear, non-subjective viewpoint, it's more like a big ball of wibbly-wobbly... timey-wimey... stuff.";
            return View(model);
        }

        [ValidateInput(false)]
        public ActionResult SaveContent(UpdateDataModel updateRequest) {
            //Do some stuff
            HomeModel newModel = new HomeModel();
            newModel.Content = updateRequest.Content;
            newModel.Header = updateRequest.Header;
            Debug.Assert(updateRequest.RandomData != null && updateRequest.RandomData.Any()); // Yields our desired result.
            Debug.Assert(updateRequest.CustomData != null && updateRequest.CustomData.Any()); //Yields an array with 1 index of comma separated values because the model binder was confused.
            Debug.Assert(updateRequest.SpecialData != null); //Will build a generic List<CustomModel> but doesn't know how to fill it
            return View("Index", newModel);
        }

    }
}

Models\CustomModel.cs

public class CustomModel {

    public string Name { get; set; }

    public int Id { get; set; }

}

Models\HomeModel.cs

    public class HomeModel {

    public string Header { get; set; }

    public string Content { get; set; }

}

Models\UpdateDataModel.cs

using System;
using System.Collections.Generic;

public class UpdateDataModel {

    public string Content { get; set; }

    public string Header { get; set; }

    public DateTime TimeStamp { get; set; }

    public IList<String> RandomData { get; set; }

    public IList<String> CustomData { get; set; }

    public IList<CustomModel> SpecialData { get; set; }

    public int Id { get; set; }

}

Views\Home\Index.cshtml

@model HomeModel

@{
    ViewBag.Title = "Index";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Index2</h2>
<form method="post" action="home/SaveContent">
    Header:&nbsp;&nbsp; <input type="text" name="HeaderInput" id="HeaderInput" value="@Model.Header" />
    <br />
    Content: <textarea name="ContentInput" id="ContentInput">@Model.Content</textarea>
    <br />
    @for (var i = 0; i < 9; i++) { 
        @Html.Hidden("RandomData", i)
    }
    @Html.Hidden("CustomData", "1,2,3,4,5,6,7")
    @for (var i = 0; i < 3; i++) { 
        @Html.Hidden("SpecialData", i) //Will not work because the model binder requires more information to build a CustomModel than an int or string
    }
    <input type="submit" id="saveFileBtn" value="Save" />
</form>