type of walking cast

I am currently in a short leg fiberglass cast with a walking boot as part of treatment for a fracture I had to the talus (nondisplaced…really more of a crack).
I am limiting my walking per the doctor’s orders, but find that it really is uncomfrotable when I come down on my heel and begin the step.
A few years ago, I had another similar cast, but it had a heel on the bottom.
I was wondering if I should ask my doctor about this kind of cast, as the weight is put onto the heel, in the middle of the foot, and is taken off the heel/ankle region where the fracture is.
Any thoughts you have on this type of cast would be much appreicated.
Thanks.Steve