Well, if I can use a 4.09, I can get the twin traction and gear set relatively cheap. I don't plan on doing any traveling with it, maybe an hour down to Woodward every year. If I used the 4.09 can I get a little large tire to make up for some of it? or is that a bad idea? I'm told there are different twin traction units for 3.92 and up, so if I go with 3.73 I'll have to keep looking.