One of the first things I do if I come up with an experimental carp/bottom feeder fly is to give it the bath tub test. I'm sure my wife loves it. I fill the tub to the top and begin dropping flies in, I look for 2 things. The sink rate is first how fast does the fly get to the bottom. Lately the carp have been feeding fairly shallow and would take a slower sink rate vs a big splash and risk spooking them. Most of the flies we've been fishing are single bead chain eyes size small and medium. The Drum have been feeding in medium depth water and traditional cruise faster then the carp so I want the fly to get to them quicker, so I prefer a heavier fly. I'll go double bead chain eyes or add some lead wraps.
The second thing I'm looking for is if the fly turns over and rides hook point up. I feel this is more important with the carp vs the drum, but plan on losing a lot of flies in the rocks. Adjusting the placement of the eyes and positioning of the legs you can usually come up with the ideal combo to help the fly turn over.
I do something similar with dry flies and a mason jar, like getting a good idea of what the trouts point of view is going to be. I'll adjust the fly to get the profile I what because I feel that is the most important aspect of getting a trout to eat a dry. This is just a test nothing test the fly better then fishing it but it gives you a nice idea of how the fly is going to behave in the water. Having fish eat they fly on a regular basis is the biggest test result of them all.