Thanks for the answers chaps. :notworthy
I run a 190/50 rear (can get them cheaper than 190/55...

), stock rear link.
Today I took a detour to have the shock checked at my suspension workshop before they shut down for the Summer vacations.
Riccardo advised to keep shock length "as is" (it's only 3mm over stock) and to only change if I "really" need quicker turn in.
He also put the shock back to its stock settings ("they played
a lot with settings"), checked the spring, the usual things...
As for the forks I have decided to go back to stock position (first line showing). Only tried it out on the stock shock (the WP is in a box waiting for a buyer...

) but quite pleased with the results. I prefer a little more stability and the bike is quick enough for me, especially with these new wheels.
Will fit the shock this weekend and be back at you if I need more advice (very likely).