I do a table top test that seems to work for me. Most of my Catskill ties WILL land upright on a table if tossed in the air. The test for proportions I like is to sit the fly on the table. It should balance perfectly between the tail, hook, and hackle tips. If the hook doesn't touch the table, your hackle's too big. If the hackle doesn't touch, or the fly lists over, your hackle's too small. I find that if my fly passes the table test, it will perform beautifully on the water. If my wings are too tall, the fly can keel over or go face down in the water. I always fight getting too high a wing, for some reason it's natural for me to want too much wing. The other thing that's very important I think, is to have a perfect "V" with your wings. The V shape will make the fly naturally float down right side up, it's basic aerodynamics. If the V's crooked, the landing will be crooked. Watch how your fly behaves in the water, and then correct that the next time you tie. Proportions are the key, but peoples ideas of proportions vary somewhat. Make the fly do what YOU want it to. You can cut a "V" in the bottom of the hackle too, but you shouldn't have to. It might make for a better profile anyway.