I've used one for decades, but have never used one in a double seat setup. I now have a Dub-L-Seat setup for my boat, but haven't used it yet. I'd check on the "leverage" aspect for you, but my boat is in storage (2hrs away) and my offset seat post is in the boat, while my double seat setup & boat seats are here at my place.
I've used my offset seat post in a 1550 Glasstream, 17' Tracker TX, and my current boat (16' Procraft ProBass) and never had any problems with the leverage weakening the floor mounts.