Is that a JB weld version of the Warren tactical grip fin ?
In addition to the Warren sleeve, I've seen people run inner tube on the grip with either a 5.56 case or more folded inner tube in the same place.
I've messed with the Warren sleeve a little, my concern about it impeding support hand shooting turned out to be unfounded but I did not see any measurable advantage accuracy or speed.
What do you like about it and what did it do for you that made you want to do a semi permanent version ?