Sharp Victory .177

[Novagun]

I have a Sharp Victory .177 which is considerably more difficult to pump, especially after about 6 pumps that my Sharp Innova in .22.
I read somewhere about enlarging the inlet port on the brass air reservoir to 3/32nds inch but I can not find the post or remember which forum it was on.
Can anyone advise me if this is a reasonable modification to make and are the benefits worth the job.

I just add that both of these Japanese rifles are completely recoil free and very accurate. They are small framed but of the sort that brings a smile on the face of the shooter.