I have a Medtronic, and originally I had a lot of issues with the site coming out. A couple of things I learned were:
1) Use a razor and shave the hair off the area.
2) Put it on after a shower so you are clean and the skin is a little more relaxed.
3) Alcohol preps really clean off the oils from your skin for a better contact.
4) IV prep makes them stick a little better.
5) Tegaderm is good for extreme cases.
6) Carry an extra because you will be ripping some out.
The other thing I noticed was it may see loos and flap while wet, but once everything drys out again, it's usually ok. They also make 45 degree sets that could go in you thigh if the vest rubbing is the problem. Beyond that, I only carry enough insulin for about 3 days max, so teh only time I really worry is if I'm riding the same day I changed the set. It's actually much easier than shots.