That doesn't sound right at all. Did you buy your P-07 new, with the original polymer captured recoil spring and guide rod assembly? It has been several years now, but I recall mine in two different P-07's being very stiff when new, then breaking in after a few hundred rounds of live fire.
I also have both the 18 and 15 lb CGW springs and they also initially start out more stiff, but break in with live fire. I run with the 18 lb ones because they give me a decent ejection pattern with my particular guns and ammo, but the 15 lb ones also worked fine, and weren't exceptionally stiff. I assume you are using them with one of CGW's stainless steel guide rods? I have had no issues with that setup, or using their springs with some titanium alloy guide rods I got from another vendor.
Generally speaking, if your gun is brand new out of the box, these guns do feel very tightly sprung... I would encourage you to go run a few hundred rounds through it with stock everything and let it break in some, to establish a baseline of what to expect out of it, before adding any aftermarket parts.