Tony, I have an HH120, but I don't have a SG2100. The HH120 will do about 55 degrees in either direction with USALS, and no problems. I've read where you SG2100 user's use the 1.2 on either end of the arc. I have not tried this with my HH120, so I don't know if it will work or not. Also, this motor doesn't have the button on it to move it east/west, like the SG2100 does. Another thing with me, was I originally used mine with my Coolsat 5000, and had problems with it not stopping on the right spot when going uphill. I'm using a 1.2m Fortec dish, so your 90cm should work better for you? I now use it with my Pansat 3500 and although it is very slow, it stops where/when it's supposed to. Of course now I give it forever (if needed) to get where it's going. Now I'm not so sure that the Coolsat was an issue, instead of my narrow patience. Anyway, I'm thinking it may not go as far as the SG2100, but Good Luck with it!
Al