o_o I dunno if it's because I ride a gelding, but I've never been in that situation before. I do, however, lean forward when my guy stops to poo because I always thought it felt weird when you can feel their backs hollow out for a few seconds and then suddenly their back 'bounces' back up. He's 'trained', so to speak, to go in the same spot every time he's in the arena, though, so it's not an inconvenience.
"There's no such thing as a problem horse. Just people that cause problems for horses." - Unknown