George,
Second thoughts...
The way my apps are working now the DE is so basically simple I don't have much need for a subclassed DE, the only thing I ever do is go set the BufferMode of the cursors, set the InitialSelected alias and the order for the parent table. I don't relations in there anymore since switching to parm-views for child tables. When I drag a field out of the PM onto a form what gets put in the DE works as is except for those above 3 properties. And if I were much lazier I'd write a builder to set them. *s*
Now this isn't to say that all environments can work like this so I still support the ability to subclass and substitute DEs visually.