I'm not sure why this sudden trend in trying to put 50cc engines in these large glow planes. The question would be why? When there are SO many great choices for 50cc applications with 1350-1450+ sq in. of wing area. They still are fairly easy to transport and fly inifinitely better than a weighed down 1150sq in aircraft. Each aircraft is intended for a certain flying weight, going above that often destroys the flying characteristics of that plane.
The thing about it is people can fly this size plane with a gasser for maybe $200-$300 less money..... The only difference between the 1.60 size plane and a real 40 or 50cc gasser is the size of the plane itself. I would for the most part put the exact same gear in either size plane....EXCEPT for the engine. A 1.60 size plane should stick with a 1.60 size (weight class) engine. The planes with 1300+ sq in of wing area are the true gassers.
Only if you can keep the overall weight down to 12 to 12.5 pounds or less should you put a gasser in the plane. Hopefully the BME 55 or any newer light weight designed engine will allow this...... Problem is going to be PROP CLEARANCE. The OS 1.60 spins an 18" prop, the BME 55 should be able to spin a 24 or 25". Even if you switch to a 3 blade you are still looking at a 22 maybe 23" prop
Blue Skies and happy landings