Very interesting replies, many thanks.

I think Geezer sums it up nicely. Received wisdom vs. actual evidence.

My conclusion is that I will hold the scope whilst pumping.

A) Because I'm putting 4 to 5 pumps in, which means light force
B) Because I'm using a dedicated one piece Sportsmatch Innova/Ace mount
C) Because I find it so much more convenient. It makes a shooting session with the Innova more enjoyable. And that's an important factor to me.

Ps. My friend Steven imported a lot of "Innova" parts from Indonesia. He might still have one or two ally breeches. They are of course not genuine Sharp parts. Probably made in China? But apparently they work well.