Kurt, I have run a 12row on a R 72 for the last 5 years. I havent added any weight to the rear. The only time I ever feel anything,is if I back up to fast,without anything in the hopper,sometimes I will feel my back tires spin free. I was going to put some in when I first went to 12 row but since I have run it dont think I need the added weight.12 head and 320 bu or corn I am already rather heavy for the wet soils. IG