Thank you very much for your advice gents.

@I.J., those are good options. However I think the Ace looks better with a 40 or even bigger objective?

@RustyBuzz, that's interesting info. I have often seen Optima Moonlighters on Ace's in eighties AGW magazines.

I might go for something modern first, with mildots, to find out about the gun's potential. The trigger is probably the limiting factor:
not too creepy (I have set it up as well as possible), but quite heavy. The Victory's trigger is much much better, but that gun is so hard to pump.

Cheers, Louis