I wouldn't be worried about doing the open practice sessions, everyone is spinning off all the time so it's all good
Just had another quick go in between work, following what Murray said I'm now shortshifting into 4th on the back stretch which makes the first 2 interesting bits pretty much a non-issue, then just lifting over the last two. I still find the right kink just before the final uphill/crest the worst bit...
Anyway, I go through Moss Hairpin in 1st, on the throttle well before the apex but only ~15-20%, then steadily increasing before shifting to 2nd, full throttle, 3rd, shift to 4th just after the left kink, then 5th at the crest of the next rise, then another crest which only needs a little lift, then the right hand kink which if you get the line right is *almost* flat but I haven't managed it yet, then job done
With the setup I've done the 2 clicks down on the rear spring rate and sorting out the ride heights, then I softened the front ARB a bit (5 iirc) which bought some of the turn in back, still understeers unless you get it sliding but that's just the way this car is I think.
Optimal now down at a 21.1 but 21.6 still my best actual lap, 0.4s of that is in the final sector alone.
I also did some testing around Oulton International as there's a UKI event there on Thursday, bit easier in terms of the straights/accleeration to Mosport, but I found several of the key braking areas are on curves which makes them really tricky in this thing