A single action revolver is meant to be fired with the pinky finger under the grip, not wrapped around it. Originally, the Colt SAA was a calvary weapon, meant for use while on horseback. Ever hear the term "throwdown" in a cowboy movie? While riding, one kept their revolver about head level, as they approached their target/adversary the arm was flung forward, thumb cocking the hammer on the way down, and it was fired. Recoil rocked the revolver rearward in the hand and up, where the rider had it ready to repeat the process. This worked great for six shots. Actually, because the gun's design left the firing pin resting on a primer of a cartridge, most SA guns were carried with five rounds, and the hammer down on a empty chamber. Paper money was often carried in the empty chamber. If you ever examine a 100+ year old revolver and find one of the six chambers to be rusty, while the other chambers are clean, often it is because paper money attracted moisture.

Google search for gunsmith's that customize SA revolvers and I am sure you will find somebody to convert your frame to a different size grip. The SASS cowboy participants have created a market for such work.