I have a dozen old dekes ! I cut the keels off except for front hole and put a foot of line with a 1 oz barrel weight crimped to the end! I'm sure you could probably get by with less decoys than you think you need!
This, I hunt water all the time just a few inches deep, sometimes only 1 inch deep, cut the keels off and leave about a 1/4 inch of plastic at the front and drill a small 1/8 inch hole for decoy line.
You will be amazed at how much movement they will make with no keel.