RE: Ace 4-120 Bipe Ultimate bash
I had a Ace 4-40 and it was designed for a 40 four cycle.
Hence the name 4-120.
I would suggest a 120 for cycle.
Saw one fly at IDA GROVE Iowa home of Byrons Originals, many years ago (1986), flew nice, but no speed demon.
Depending on what engine you use.