How to get WebAPI XML serializer to use TypeConverter - asp.net-mvc-4

Question

In a ASP.NET Web API project, I've got a custom type with a TypeConverter that handles the to and from for string conversions, as described here:
http://blogs.msdn.com/b/jmstall/archive/2012/04/20/how-to-bind-to-custom-objects-in-action-signatures-in-mvc-webapi.aspx
The custom type is used as a property in my model and this works great. The json for my model object includes my custom object as the string value created from my TypeConverter.
So then I switch the request to accept XML instead and the TypeConverter is no longer invoked and my object is incorrectly serialized.
How to I get the XML serializer to utilize the TypeConverter as the JSON one does. The article referenced made it sound like the use of TypeConverters, when present, was a predictable feature. If it is completely at the whim of the serializer then making APIs that express data in both XML and JSON in a consistent way is nearly impossible.
Sample code from the article, plus a bit of context:
[TypeConverter(typeof(LocationTypeConverter))]
public class Location
{
public int X { get; set; }
public int Y { get; set; }
// Parse a string into a Location object. "1,2" --> Loc(X=1,Y=2)
public static Location TryParse(string input)
{
var parts = input.Split(',');
if (parts.Length != 2)
{
return null;
}
int x,y;
if (int.TryParse(parts[0], out x) && int.TryParse(parts[1], out y))
{
return new Location { X = x, Y = y };
}
return null;
}
public override string ToString()
{
return string.Format("{0},{1}", X, Y);
}
}
public class LocationTypeConverter : TypeConverter
{
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
{
if (sourceType == typeof(string))
{
return true;
}
return base.CanConvertFrom(context, sourceType);
}
public override object ConvertFrom(ITypeDescriptorContext context,
System.Globalization.CultureInfo culture, object value)
{
if (value is string)
{
return Location.TryParse((string) value);
}
return base.ConvertFrom(context, culture, value);
}
}
Create a model with that class:
public class SampleModel
{
public int One { get; set;}
public string Two { get; set;}
public Location Three { get; set;}
}
Create a ApiController with a method like this:
public SampleModel Get()
{
return new SapleModel { One = 1, Two = "Two", Three = new Location { X = 111, Y = 222 } };
}
That's it. Using fiddler and try them both and note that Location serializes using the converter into the single-line comma-seperated format like this (Three="111,222") with Json but not with XML.