Like Boll Weevil, we found an older Great Plains twenty foot three point drill and cut it down to ten feet after the first fall. Ours does a great job of metering seed mixes, large and small seed together. This one is very heavy...2000 pounds plus the caddy it is mounted on. Six inches between rows so canopying is quick for weed control. After cutting down we have plenty of extra row unit parts. Total cost ......$1100.00Believe it or not that old drill cost me $1400. Might take you a little while but hunt around till you find what you can afford and what meets your needs. Yeah it's older equipment but it gets the job done with an efficiency that just can't be matched vs. running back and forth to pick up different pieces of equipment on a big piece of property.
Good luck to you!
I hope you find your solution.