MVC4 Partial view not loading values into "container" model on post back

So I want to create a re-usable view for editing an Address, phone number, etc.

I setup a Container Model that contains all the Models needed. Created a partial view to handle the Address part of th e form

But when it posts back to the controller, customer data is there from the main page, but anything from the partial views is not there (using MVC4/Razor)

Container Model

public class CustomerViewModel {
    public Customer CustomerData { get; set; }
    public Address MainAddress { get; set; }
    public Address ShippingAddress { get; set; }
    public Phone MainPhone { get; set; }
    public Phone Fax { get; set; }
}

Controller:

public ActionResult Edit(int id = 0) {
    CustomerViewModel model = new CustomerViewModel();
    model.CustomerData = Customer.FetchById(id);
    if (model.CustomerData == null) return HttpNotFound();

    //... load addresses, phones

    return View(model);
}

[HttpPost]
public ActionResult Edit(CustomerViewModel model) {
    if (ModelState.IsValid) {
        ///... save everything here - model has CustomerData, but nothing else
    }

    return View(model);
}

Main View:

@model ProjectName.WebSite.Models.CustomerViewModel

.....

@using (Html.BeginForm()) {
    @Html.ValidationSummary(true)

    <fieldset>
        <legend>Customer</legend>
        @Html.HiddenFor(model => model.ModelCustomer.CustomerId)

        <div class="editor-label">
            @Html.LabelFor(model => model.ModelCustomer.CompanyName)
        </div>
        <div class="editor-field">
            @Html.EditorFor(model => model.ModelCustomer.CompanyName)
            @Html.ValidationMessageFor(model => model.ModelCustomer.CompanyName)
        </div>

        ...        

        @Html.Partial("Address", Model.MainAddress, new ViewDataDictionary {
            TemplateInfo = new System.Web.Mvc.TemplateIn