Welcome Otto...were getting quite a clan in here !!! SP5..dribble dribble...!
Ref the swingarm, have you thought about replacing it?? Ive seen a few on (german) ebay the last few months from early monsters (which use the same swingarm I believe). Its going to be difficult to retain that satin finish with polishing. Your idea sounds OK ??
Not sure where your marks are but have you got the michelin stickers on?? These will hide a good deal of the scratches and were standard fitment on the SP5 from new, so your remaining faithful to the orginality !!! (see attcahed picture from 888 sales brochure).
BTW..if your single seat units missing one night it wasnt me or celeste OK ???
(I priced up an OE unit and it was £680 with seat pads..gulp!)
Hopefully well all catch up in the summer !