HI RICK, This might be my favorite subject. I've always thought that one of the coolest things that a model can do is "thumb its' nose at gravity" and go straight up till you can't see it . A model can't be said to be able to "do it all" if it doesn't have unlimited vertical. It sure is good to have a beforehand idea of what we're playing with for thrust. I don't know what the breakoff point is where a model doesn't have enough thrust to accelerate straight up, but it has to somewhat less than 1 to 1.

I have measured .049 BABYBEEs at 9 ozs of thrust. An AME .061 checked in at 24 ozs. I think I got a best effort of 18 ozs from a BIG MIG .061. I haven't bench tested the .074 NORVEL, but it will take a couple of 16 oz models I have straight to JUPITER. I think a typical $60 sport .15 will go vert with 28 ozs.

As far as matching these engines to airframes [ and various wing loadings]goes, that is a matter of personal preference. Kit manufacturers want their planes to seem as versatile as possible so that is why you will see quite a wide range of recommended engine sizes listed. You also have to look at the airfoil when deciding which engine will suit the plane in question. I have a 40 oz plane with a lifting airfoil that flies nicely with a .15. It is very lively, it is actually a rulebook combat plane. It just doesn't have much vertical. Maybe I'm giving you too much info here... to answer your question as direct as I can, aim for 14 ozs for a .049 to .061 powered plane, and 16-18 ozs for a .074 powered plane, but if you want to go lighter, that's OK with me!