I've just bough a secondhand Classic seat but it doesn't quite fit straight on my 2010 Roadster. The rear separate pillion mounting bracket is about 10mm too long , so the "spike" for the click-on seat catch is 10mm too far back for the seat hole. I'm about to re-drill the 3 front holes for the allen screw fixings to the mudguard, with some spacer washers, to bring it into line then should work OK.
No idea why there's this 10mm difference, but there it is.
The rider part front mounting spike is correctly placed, and without the rear bracket the Classic seat sits in place end clicks into place fine, but as soon as the rear bracket is fixed it won't fit!
And yes the rider's position is a bit lower, but the pillion is about the same so my wife can see over my shoulders better. Roll on better weather to ride in!