Of GSP magazines and wells

I've heard rumors that the contemporary gsp expert can take lightly modified p22 magazines.

Also allegedly the 80's gsp can be (gasp) modified to take the new gsp mags, and by extension also modified p22 mags.

Can anyone lay hands on any of these and confirm, deny, or illuminate these allegations?  Just how different is the gsp and gsp-expert magazine well?

Contact Earls Repair Service http://www.carlwalther.com/page1.htm.   Earl can mill the magazine well for the older GSP's to accept the newer ribbed magazines.     He milled my 1973 GSP and I now use both the old magazines along with the new ones.    Both work equally well in my GSP.   Money well spent......