Oh man, I've had to patch so many crotches already. The first time I found it really difficult, because of having to fit patches to a curve. It's been getting better recently. I find it is also better to do several small patches, because if you make one that reaches from front to back, it is much harder to figure out how to make it fit properly. That, and since your new material is strong, all wear is gonna probably happen where the new stitches go into the plans. Usually this is already pretty worn, so will tear sooner or later. No problems, just keep overlapping patches, as genghis braun said.