Big Bores again, problems.

[Dandare]

Getting tired of shocks, lol.

My problem is this, bearing in mind big bores have no bleed hole etc.

I fill body with oil, so it just creates a 'dome'

My aim is to set with minimal/zero rebound. I put the cap on only 1 turn or so & slowly push the shaft so almost fully compressed, do up the cap, what happens is i get 100% rebound, not good.
So i repeat, still 100% rebound, basically, the only way i'm able to reduce the amount of rebound is to remove oil.
For example, to get zero rebound i have to do the cap up with the oil 3-4mm below full but i then end up with lots of air inside & i can feel the air too ie, a few mm's of loose play with no damping.

I know the thread seals well even with the cap almost undone so i have to almost have the cap off in order to release oil.

I can't see how i can set these up without a) introducing air or b) having way too much rebound.

Any ideas appreciated