This sank out of sight instantly in the other section so I'll try it here.
78 CB550 clutch.
This may be a shot in the dark but has anyone eliminated the rivoted double steel plate in favour of an extra disc & regular plate? This was Hondas attempt at a quieter improved clutch, but this is for a race engine so quiet doesn't help but a larger stack might.
Once the bike is running I'll try it, there may not be enough play but just measuring looks like when totally disengaged the extra disc option yields 2.1mm free play, the stock 78 gives 3.33mm, and an earlier model 550 3.79mm.
I stacked all three into one pic trying to show available space disengaged, hopefully it's clear.
Left pic-extra disc, center- stock 78, right - earlier model 550 with Barnett discs.