On my Mossberg 500 20 gauge I currently have the stock wood forend on it, I'm wanting to get a vertical grip for it. I know I'll have to replace the forend. My question is, I'm not finding any for a 20 gauge. Would those for a 12 gauge fit? I'm thinking one like this http://www.ebay.com/itm/Mossberg-500-590-Forend-With-Vertical-Grip-and-Picatinny-Rail-12-Gauge-Shotgun-/190843504456?pt=LH_DefaultDomain_0&hash=item2c6f28c748. I emailed asking the seller but I want to know from those on here. My forend on there right now measures 9" and is held on by a spanner nut in the front if that matters.