Before I got half way through your post I was thinking to myself "he ought to try soybeans" and about then I read where you do.
We have thousands of acres of deer plots, but we wish the deer would stick with native forage. We actually try to harvest the deer plots for profit. We have what sometimes from a distance looks like a cattle herd grazing on soybeans.
You might also try just a small amount of corn seed mixed in your plot seed mix. Not a lot, just a little. It will give fall grazing. The deer really like the corn as it hardens up just beyond roasting ear stage all the way to harvest stage. They eat the tops off the ears and will eat some shucks when the corn is younger and the shucks are still green. The corn stalks standing up will also give some cover. You might find a farmer that has old seed to get rid of. Corn seed runs anywhere from 200-300 dollars for a bag of 80,000 kernals. With a 40' planter it is nearly impossible to end up with less than a bag or two wasted at the end of the year trying to make the last field planted "come out just right". Unfortunately lots of times it is more like 5 or 6 bags. We will save that seed and use it to finish up the next year, but we never save it over a single year so we nearly always have some bags of 2 year old seed siting around. Then we have to bury it to properly dispose because of the seed treatment involved (can't be used for feed). If you find a farmer with some seed like that, he likely will be glad to give it to you. The germination might be anywhere from perfect to as low as 25%, but enough will grow for your purposes. I would try to shoot for a stalk every 3-5'. Not so thick it shades out your other planting. Just an idea. I've never done it specifically to feed the deer, but they sure like the edges of our fields or any opening within such as a wash where they can walk in a ways.
