Victor,

I would think a Saito 1.50 is too heavy- is made on a larger framed case, if you are to consider a 4 stroke look into a YS 1.10 or Saito 1.25. Run either with 25-30% nitro if possible.

In a 2 stroke I'm not certain a Supertiger 90 would give you much performance advantage over a piped OS or YS 61. The OS 1.20AX is very powerful and weighs less than the above mentioned 4 strokes, if need a boost over the piped 61's this would be your best bang per buck. No one in my area has an Evolution engine so I cannot comment.

Good luck & let us know what you decide.