I would generally agree that the MOE forend works well. I have a number of them on other 870's & a 590 that I own. However, I don't much care for the looks or the placement of the vertical grip (based on its distance from the mag tube) of the configuration. With a higher center of gravity (relative to the grip placement), I want to minimize the amount of potential roll-over in the hands from it being too top-heavy. That's my biggest concern.
I've got all the individual components (short of the grip) to build the MOE configuration to give it a try before spending a lot of money. I know I'll want the grip regardless, so I'm just going to buy it and see how it goes.
So far, Dlask is the only option I have to get what I'm looking for. Ergo hasn't bothered to reply to my email so I'm guessing it's a no-go.