One of the things that was part of the problem was finger positioning on the draw. As slavex pointed out that you need to press in to release the gun and that your finger might hit the trigger.

That pic shows where you finger is after the draw even if you had a tight grip it is not going to pull the trigger.
http://youtube.com/watch?v=NqC4hJy7Gfw
Video of draws from a SERPA for a 1911
http://youtube.com/watch?v=ZLVImT-UmCg
Video of draws from a SERPA for a XD40(note: it is awkward to draw from a canted holster well holding a video camera with the other hand)
I do not see an issue with the SERPA's.