There have been some safety concerns with the FDPCP recently.Converting your QB to PCP' would be far better choice.And for what it's worth, yes I own both guns.The QB is a much better gun. IMHO.
There is a modification done to the XS60C which can be used with a magazine done by Stalwart Arms.http://www.stalwartarms.com/Also from Stalwart Arms is Disco double tube and can be won in the GTA raffle. Who knows you might win. Also just on the market is the Benjamin Maximus.http://www.airgundepot.com/benjamin-maximus-air-rifle.html
I've got both currently, and I prefer the QB79 pcp with ninja shp regulator over the fdpcp. In the sweet spot of the power curve the FD is slightly more accurate at 50 yards, but I am now spoiled with the regulated gun. Tuned to 775 fps with 14.3g cphp, I get nearly 100 shots from 3,000- regulator setpoint. I get around 25 shots with the FD tuned for a 850-899-850 string using 7.9g cphp. Also, the trigger group housing on the FD cracked after about the 3rd time tightening the rear bolt...as there is a gap in between the receiver and trigger housing. Too much torque and it bends the cast pot metal, and pot metal doesn't bend too well. Both do have pretty nice triggers when adjusted properly.