Got to mess around with a gun with a Lanco TacticalGrip Stop Mod2 today and I think I liked it much more than my MOE stubby (sawed off to about 2")
http://www.lancotactical.com/product_p/ltgsm2.htm

Question though, is there a cheaper version that fits picatinny rails? I'm seeing a bunch of good looking Keymod versions but $50 is cheaper than a new rail (and Lanco no longer makes it). I'm looking for the slope and height of this. I threw away my MagpulAFG because it felt like shit when I was shooting..... So no I don't want an AFG

It's now manufactured by B5 Systems. We are expecting the Picatinny version to be released soon.

I'm friends with the inventor of the Gripstop. I have one on all my rifles...including my UMP clone. You won't be disappointed with the money spent on it. They are rock solid and as you've seen very comfortable. Our mutual friend has been doling them out to guys in 5th Group and 20th Group. They all love them too.

If you're patient it'll be worth the wait.