It's too small. That's a ram 500 sized model. You may physically get your 750 to fit... but you won't be able to properly duct the thrust... and you won't have any room for fuel. You may have 18 Lbs... but it's a thirsty engine because of it's inefficiencys. SO... you need to be able to carry +70 oz of fuel for a 4~5 min flight. The Wren 54 (the ideal engine for it) only needs 50 oz for a nice 6 min flight.
Please don't take what I'm saying about the older RAM in a negative way. BUT... you have to think about the airframe it will work in.
I just downloaded the manual... and it's really meant to fly on a Wren 44. So... you would only have to carry a quart of fuel... and it would be nice an light. Also... it's saying to turn down engines making too much thrust. (more than 14 Lbs?)