Couple suggestions:
1. Cut away a little more leather where your fingers go around the grip of the gun. You want plenty of clearance there so that you can get a good initial grip of the gun.
2. Sandwich your T-nuts between the two layers of leather.
These type of holsters are not traditional or pretty, but they are comfortable and they work. When forming Kydex, you may have to tape something to the top of the slide behind the front sight so that the Kydex will form with a sight channel.