RE: zenoaoh G-38
This really depends on your flying style. With an 18x8, the '38 will make about 17 pounds of thrust (static). That'll make a pretty marginal aerobat, but for a put-along, it'll work just fine!
What do you want your plane to do? She was supposed to be a racer, and in level flight it should be pretty well motivated. Not real quick, tho, with the 18x8, you're looking at flight speeds in the 50-60mph range.
More pitch will give better flight speed, but at the expense of thrust.
Pretty model, that!
J