I'm not sure that the Laser Max Guide Rod would work with the .22 LR conversion for you Sig P226. I had a Laser Max on my Glock 26, which has a captive spring. I'm assuming that your .22 conversion either has a spring and guide rod or a spring that you have to change so that the recoil of the .22 can cycle the gun. If the spring goes over the guiderod, then it might work. I suggest you call them directly.
I did not like the Laser Max for my Glock and ended up taking it out. On Glocks, the laser is activated by pushing the lake down latch to either side of the gun. The wider take down latch made it difficult (or impossible) to use with most holsters. I also activated the laser quite a few times accidentally and had no juice when I wanted to use it.