Re: Swivel Seat Base Q?
It's highly likely that you would have to fabricate an upper adapter plate and a lower adapter plate (or drill new holes in the floor). Take a peek under your seats and look at how the bar for the slider mech hangs down. Whatever base you end up with has to be able to mount to the seat and allow that bar to move up and down to adjust the seat, so the adapter plate won't be a simple 2D flat plate, it needs to be bent/joggled vertically to allow clearance for that bar.
On my 2008 there is also a seatbelt retractor box that needs to get relocated; your 2011 may or may not have that.
2008 E350 RB passenger 4WD SMB penthouse
2013 KTM 350 EXC
2008 KTM 250 XCF-W
2000 KTM 200 EXC
2003 Honda Element