I think what conor is refering to is a "heel"... the things that sit on the bottom of a pistol grip.
For me, flexibility is in FT is quite important, and the benefits of such are probably compromised by this factor... to add, most prone shooters have dispensed with them.
At best i think it's a marginal gain, but probably not something that most people would see a benefit from, and it would have to be looked at quite objectively. But like anything, if it works, more power to you.
BFTA/NSRA County Coach
CSFTA Chairman/BFTA Rep