RE: plane weight to engine sizing chart.
Hi Big Mo, I dont know about weight and size ratios, but if you have a zenoha 20cc it will go in a seagul extra 1 20 size I have this set up and test flew it on sunday and it flew much better than I expected. This set up gives a very good SPORT performance. The total weight came out at 12lbs. I put a 3cell ignition battery in, 3cell is what they recommend . I managed to get hold of a 6,500 MAH which gives loads of running time and the bit extra weight just works out for the c of g. Hope this has been of some help. I love my little zen , they are a great little engine , not a lot of mess either. Happy flying . Regards Bill.