Several years ago I bought a used CG Extra that was being flown with a ST 90. Overall performance was good, but vertical was marginal. Replacing the ST 90 with a Thunder Tiger 1.20 made a big improvement in the vertical performance. The TT 120 gave it enough reserve power to pull out vertically from a hover.

I also have an OS 108 in a CG Ultimate. The TT 120 and the OS 108 weigh almost exactly the same, but the TT 120 has more power.

IMHO, if you want a two stroke for your Extra, the TT Pro 120 would be hard to beat.