It goes by wing area. Find out what area you want for the new engine ( this part is just research and comparisons. There's no formula) and blow up the plan to match. It's a square root relationship. If the new size is 1.6 times the area of the 90 Kaos then the linear scaling dimension is sq rt ( 1.6 ) = 1.27. So you'd ask Kinkos or whoever to blow up your photocopy by 1.27 times.

I suppose there IS a guide for how much area. You'd have to graph 60's, 90's, 1.20's and up to your engine and maybe a little larger and then join the points with a graph curve to figure out what area you want for the new engine. But it's only approximate as different folks want different models.

The numbers are up to you as I don't have anything over a 46 that I fly but a graph of that sort will answer a lot of questions.