For those of us who have to "Elvis Costello" their PCP.

I'm starting to wonder about the air tube volume being a big deal. If an average .22 needs 2 pump strokes per shot, the air tube doesn't matter. Even more so if it's regulated. You can shoot 24 shots and pump 48 strokes or get a big air tube and shoot 36 then pump 72 strokes. It's still 2 strokes per shot. 

The exception would be the the day you are surrounded by more than 24 angry squirrels at once or if you were trying to shoot a full FT match without pumping.