The SK 1.10 and 1.30 2-strokes sold by KangkeUSA are good alternatives if you're shying away from the pricetag of the O.S. Max 1.20 AX. Both SK models are slightly heavier than the 1.20 AX, but are powerful, reliable, and a great value.

The Thunder Tiger Pro 1.20 SE (Side Exhaust) is almost five ounces heavier than the 1.20 AX, but it is another very good value in a top quality engine.

The Magnum XL 1.20 AR-II is another solid choice that is very close in weight to the O.S. and a good value for the price.

Sig carries the Aviastar 1.20 2-stroke, which is almost the same weight as the 1.20 AX (within about an ounce or so). While not a well known brand here in the U.S., reviews of Aviastar/Aviatech engines have been positive. Considering the Aviastar costs almost $100 less than the O.S. Max, it would be a very tempting engine to try.

To find something lighter and more powerful than the O.S. Max 1.20 AX, you don't have very many choices here in North America. All of the commonly distributed engine lines seem to be slightly heavier than the O.S. model.

If you want power and light weight in a 1.20 2-stroke, the 1.20 AX really appears to be the best option.