I did mine about a month ago and and had no problems making the cuts with car on jack stands. I used some fence wire that I had to tie the rear exhaust in place so it did not move when cut (and keeps the tips aligned as the pipes can't drop). It's not hard to get straight cuts with a sawzall if the blades are new and saw is braced firmly against the piped slowly rotated. I think the whole job took about 15-20 min from start to finish.
I didn't have any issues with the clamps, but obviously don't have a lot of time/ miles on it .... no leaks however.