Decades ago, I bought a Safariland 100/101 (one of those is for autos, the other for revolvers, can't recall which is which) for my 6.5 inch model 29. If it's still in production, go for that as first choice. It uses surgical elastic for retention and still holds as tight as new.

I have a X-15, it was originally developed for the 1911 .45. Been a pretty poor fit for anything else.