You should be able to add a rail section to the bottom of the OE hand guard. As was said above, I'd try one of the AFG before buying. I thought they looked pretty cool some years back. A friend got one and let me try it. To say it was uncomfortable was an understatement. I'm not a fan of fore grips anyway, but I find a standard vertical grip more adaptable as it gives you a number of options for hand placement.
As a brace similar to an AFG
Simply as a vertical grip
Or as a hand stop
There's my 2 cents.
