I used a WGP sledgehammer in at least two of my personal pneumags in the past. They were both set at about 35-45psi and worked fine.
I'd have to dig through AO, but I think it was graphed at like 17+bps burst peak with 15+ sustained.
A few things can be done to increase the volumes. An inline volumizer can be placed on the output to increase the LP volume, larger hoses can be used to increase LP volume, or the adapeter can have a larger volume in it to increase the HP volume. If any problem does indeed exist for this reg outputting ~25psi, optimizing spring rates will be the best performance increase.
I don't think volumes are the problem. The primary disadvantage of the WGP regs is the small piston diameters.
I should have the first production adapter done sometime this week when my threading inserts arrive.
I'll finish the frame and ship it back to the owner for testing.