Hi Craig,
Two ideas, one easy, one lots of work.
1. Use the MOUSE command to simulate a click and drag resize.
2. Implement your own docking form framework, i.e. create a class of forms that behave similar to VFP docking forms, but with your extended behavior. Thanks to your demos, there's a lot to like about dockable forms, and yet, to me, VFP 9's dockable forms still have that 1.0 "almost, but not quite finished" feel.
Malcolm