If you don't want to mess with the retracts, leave the retract servo out, pull the retract pushrods together as far as they will go (fully into down lock) and use two wheel collars to keep them that way. Voila; fixed gear.

If you like the Rambler 45, get it.

OBTW, the Rambler 30 is much harder to fly than the Rambler 45. They are not the same design at all, and the 30 has a higher wing loading. I know, I had both.

Jim