UIHint not working for Edit.

Question

I have the following metadata declaration in a NotificationTemplateMetadata class used in the [MetadataType(typeof(NotificationTemplateMetadata))] attribute for my NotificationTemplate class. In this class, property ExternalRecipient1Sms is a string with max length of 800.

The metadata:

[UIHint("MultilineText_Edit")]            
public object ExternalRecipient1Sms { get; set; }

In the List and Deatils views, ExternalRecipient1Sms gets a nice large multiline textbox, but in the Edit view it gets a single line textbox 300px wide, which is useless to me.