As you all know, I believe strongly that Pilates can be hugely beneficial for everyone. In the past, I've seen students shy away from classes because they felt as if the movements weren't designed for their body-type. Here's what I have to say to them: It's not the movements are wrong, but the pacing is probably off.
If you've been nursing old injuries or you naturally carry a little extra weight, moving quickly through Pilates poses isn't going to work for you (at the beginning). Sticking to a slower pace, and concentrating on the fundamental principles of alignment, will allow your Pilates practice to take flight. Taking the time to ease into poses, and modifying when necessary, will not only keep your body safe...it will also start the process of re-patterning - where the muscles learn how to move more efficiently, and strength develops to maintain proper alignment even outside of the Pilates class.