By design, the Benji gunframe is already a spring

You know this because the POI changes with increased pumps.

Now I am betting that there is a heck of a lot more tube and barrel spring going on with Phil's SSP than with a stock Benji seeing how much pump handle pressure Phil needs to apply in order to crunch the gas.

Tube and barrel bending might not mean a hill of beans for MSP format but an SSP shot charge may welcome the additional boost. So in theory, there must be some boost otherwise how is the barrel bending explained.