Hi Louis, I'm really excited about this Innova, like a Benjamin/Sheridan but has a much better way of scoping and moderating.
I see the alloy breeches like fitting the Crosman aftermarket steel breeches on the 22 series.
I'm also not sure about the oring type piston seal, they tend to damage easily. This one was nicked when I removed it and I've ordered some heavy duty ones to try. The first thing I did to the tube before blueing was sand inside the cylinder with fine grit wet and dry, to remove any burs. The burs are especially bad around the pivot point holes.
As ped says I also think the two mating surfaces of the piston and valve are mismatched when fitting the trobb head. This could caus increased head space and a rubbish seal.
I will see how It goes but I may have to do as you've done and fit a good quality pump cup.