I switched from the Serpa to the Safariland ALS paddle holsters for this same reason. The Safariland paddle is shaped to fit your body, whereas the Serpa paddle is almost like sticking an oven pan down your pants.
A slight reshaping of the paddle using a hair dryer might be worth the effort.
GF has a kydex holster (not Serpa) for her P9. No amount of break-in loosened up the snap-tight fit enough to cleanly draw the gun - we both spent a lot of time with attempted presentations. She most often either came up with the holster and gun + a sore hip. I finally started succeeding w/dificulty after 100s of draws and liberal lubrication - not good.
Spent some time with a hair dryer, paddle fits much better with the new bends and by heating the kydex holster body w/empty gun in it, twisting the gun side to side while wrapped in paper towel, when it cooled sanded down the retention "bumps" very lightly and Bingo works like a charm. Good retention requiring a precise draw motion, but very quick presentation.
If you do try this be patient - a little at a time is the way to go.