I had the same thought before I put together my 6" G20LS. I found that even light 40 powered 10mm reloads functioned fine even with the 22# spring. The G20LS weighs about 25% more than a factory slide, so that slows down the cycling even more. You can get ISMI springs for $8 shipped on eBay, so they're more than cheap enough to just buy a few & calibrate your gun the way you like it.
GEN 3 20LS/20SF/21SF/30SF/23/34/26
GEN 4 17/19/21/34/35