Hi, this might help.
On the photo is an unscoped Innova, but with a scope on your Ace you will probably still be able to hold the stock and the scope together in one hand.
What I learned from this photo is to put the butt on my right upper leg, whilst bending my leg a bit. It makes pumping a lot easier. And never hold the wrist of the stock.



This is a photo of what I mean with my Victory



Cheers, Louis