The only foot system I've found--the perfect one I think!--that allows me to climb with my foot flat and receive maximum gain with each step is with a Gibbs ascender positioned tightly right on top of my foot. The strap is as tight as you can make it, so it seems one with the boot, so there is no slop in the foot strap. Also, there is minimal slop in the cam attachment. This way the force of stepping is through the center of your foot, as if riding a bicycle with the pedal under your arch. Climb with a slight bicycle motion--kicking a bit forward--or kick a bit out to the side to ensure the cam grabs with every step.
I reached into a box of vertical gear and pulled out the first foot rig I came to, put it on my shoe and took some photos.
A couple of notes:
--The buckle can be sewn on either on the inside or outside of the foot (just below the cam.) It is up high enough so that it doesn't get pried open when walking.
--The red 1" webbing needs to be stitched with a sewing awl since it is under the eye of the cam and the webbing needs to be as taught as possible.
Gary S., try it and tell me if I win the prize!