I took a similar approach to the others with a few changes.

Parts:

(2) 9" X 13" X 1/4" Aluminum Plates
(1) Swivel
(4) 1/4" - 20 X 3/4" Bolts
(16) 1/4" Washers
(Eight) 1/4" Locknuts
(Eight) 5/16" - 18 X 1" Bolts
(2) 5/16" - 18 X 2 1/2" Bolts
(4) Factory Flange Nuts (Originally held seat to rails)
(12) 5/16" Washers
(4) 5/16" Nuts
(2) 3/8" Nuts
(2) 3/4" X 1 5/8 Aluminum Spacers

My factry seat did not have holes in the center to attach the swivel to, so I mounted one of the plates to the bottom of the seat using 5/16" -18 X 1" bolts, washers, and factory flange nuts.




I then drilled thru the plate into the seat. The seat was hollow in that area, so I drilled the top out to 3/4" so that a socket would fit in to hold the nut.




I set the other plate on top of the rails and shimmed up to make the plate even with the floor. The angle worked out to be 6 degrees.




I set my adjustable square to 6 degrees and mounted it to my surface grinder.