Feet

I opted to go with Vex Omni wheels for the center foot.  

Using a combination of Kevin Holmes Vex bracket and a DIY attaching harness, the center foot was built in a few hours.

For the outer feet, I decided to go with the DDRIIs.  Boy are they heavy beasts.  I applied spacing chipboard to the top of the drives to achieve the right clearance height.  The only piece of wood on R2.