what about
putting the pullup on the outside of the brace instead of inside?
There are worse things than being 4 and not potty trained if it comes down to it. My 7 1/2 yr old is finally able to recognize when he has to go (he lost large portions of intestine at 3 1/2 months of age and as a result has had nothing but watery diarrhea anywhere from 15-20+ times a day until recently). Kids learn when they are ready, and for some its 2 or 3, others its 4 or even 5. In my experience with 3 boys, none were ready at the same age, but when they were it only took a few days for them to get it and were ready for big boy pants.
Good luck.......
Heidi
Heidi (mom to 3 boys, Sean is 9 and has LCDH, SBS, is TPN, O2, and Bipap dependent, has SVC stenosis/stent x4, severe malignant scoliosis fused twice from T1-L2, halo traction for 2 months, severe restrictive lung disease, a CVL and GT, Fundo x2, and is one of my heroes.)