You still watching this thread Joe?
Many of the white clovers like durana tend to prefer clay soil over sandy.
I suggest you give plain old medium red or even some crimson clover a try. Crimson clover is not too well liked by deer, but in poor soils it is good to have something that is not eaten to death. A good shot of 2,4D would close to wipe out the clover.
I planted some milpa seed mix from green cover. I saw some clovers doing well that i did not recognize at camp, zone 3 sandy soil. Almost junk sand spots. Milpa has persian clover in it. Aslike might be ok too.
Plantain is a chickory like plant that does well in poor soils. I have it at camp in high traffic areas, like the camp lawn and parking lot. Deer n snowshoe hare love it.
MY plan at camp is to let the weeds win. I will plant rye and oats, but let the weeds be until mid august or so. Then one year I mow or knock it down and the next I use roundup. Always plant small grains, a few different clovers, and a small amount of brassicas like 1-2lb an acre. Clovers are about 8lb and acre and grains are about 80lb. Uusually 2-3 parts rye 1 part oats. I get wheat dirt cheap even sometimes free, so I sometimes add a 1/2 part to the mix. Wheat needs to be in the ground more, but can make it some no till years. I have a nice tow behind set of discs for the ATV, so might be more min till now.