CjR, I don't think you're going to be all that much better off with the AG tires in that rue. The CK20 has a 12" clearance, and you'll be on the bottom at 14 regardless of the tire. Sometimes, I've found that the wider R4 can stay on top a little longer than the narrower Ags unless I do a lot of back and forth in the same rut, and you probably know what that does, but they will fill up with mud and then most of the traction is gone.
I've never been able to stick the tractor all the way yet as long as I have my loader. I just get that bucket rolling and curling me right out of it. I have been on the bottom of the tractor, but I have always gotten out so far. John
EDIT: I just read what you posted while I was posting mine, and for sure if you're going to the wood to drag logs, get the larger CK20 or equivalent rather than a Sub CUT. The extra clearance will make a lot of difference, and the CK20 does a great job of pulling large logs. You may have seen my post on pulling logs where I was pulling some over 20' long and two feet across. Not bad for a small framer. John