So I was adding the mainspring from the scopesandammo Phantom repair kit to a Phantom and I was disassembling a Benjamin Classic at the same time to examine the de-tuning methods. As it turned out, both were detuned using a weaker spring. Anyways...

Still having my spring from the QB57 repair kit, I took it out and compared it to the mainspring from the Phantom repair kit. Well as it turns out, the QB57 spring (with 0.25" of it removed) is exactly the same dimensions as the Phantom mainspring.

I'll let you know how the Classic compares to the upgraded Phantom tomorrow.