So I thought after we talked I'd revisit the Famicom jailbars and realised that with that upgrade installed, the cap across pins 20/22 of the PPU actually make NO difference at all.
When I was picking up video direct from pin 21 of the PPU it did make it look better, but when the PPU circuit is as normal (As it is for this upgrade) that particular jailbar fix is redundant.
As it goes the current jailbar situation is as I said, only really on big blocks of blue and is equivalent to the direct connect to the PPU via pin 21 with a comp mod WITH the cap, so it's really OK.
I will have a look though, see if there are any other options for improvement.
I'd still recommend the upgrade though

