| As above, get a bracket and drill the seat unit to bolt through it.
Use your standard seat pad if poss and theres no need to fiddle with nuts and bolts.
If your not using the standard seat then you will have to bolt it to the track seat unit by drilling it using a template made from your standard seat unit if youknow what I mean?
Careful with the screws you use to mount it to the seat unit.
They need to be countersunk or they will foul on the locating pegs as you try to locate them.
Use the standard screws if your using the seat pad, buy countersunk M6 x 8 or 10 if not and use some big washers on the seat side of the unit but make sure they dont catch the tank! | 
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