I have a YS 140 DZ on my DPM Ultimate 120. Here's a video of it:

http://www.pedrofrigola.com/Ultimate%20Show.wmv

My DZ swings Pro Zinger 18x8 @ 8500 rpm, which is a little stronger than Saito 180, I think. But I am sure Saito 180 swing a Menz 18x6 will haul it around just as good.

By the way, my 2-lb engine makes the DPM Ultimate nose heavy. When I have cowl on, I have the battery pack at the tail to balance it at the middle of the CG range. Saito 180 will be perfect, as it is a little lighter than my 140 DZ.

Joe,
With a Moki 2.1, I don't know how you would balance the plane. It's not like most other 1/4 scale aerobats with 3 servos mounted at the tail. There is no servo mounted at the tail. This plane also has a short landing gear, so 20" prop wouldn't fare so well.