The raptors are great for making legal length but they need a different profile to support the hand closer to the trigger. I have one on an 870 and compared to a speedfeed its night and day for grip position relative to the trigger. I built up the grip with some tape to be more comfortable but the best thing would be some epoxy putty to te shape the grip and support the hand in a better position.
I haven't tried one on a mossberg but I can only imagine it would be worse due to the already longer trigger reach of the mossberg design.
Speedfeed witness protection is my favorite grip for comfort so its not like I don't like "birds head " grips.
Get the raptor if you need a pistol grip for a 14"er but be prepared to reprofile the grip for comfort! I used some foam strips cut and contoured with hockey tape over top.