If you wind up with a unit that does roll up the odometer, you might consider the following:
On my ROCKY the odometer does roll up. I keep a spreadsheet on all my vehicles to track taxes and MPG among other things. I fill one cell with miles being towed so I can subtract from the total miles and therefor have the number for the miles actually driven.
For instance, we visited Jellystone NP and the towed miles was 1250. The miles driven in the park was a couple of hundred.
The original owner of my ROCKY also used it as a toad so the 80K miles on the odometer was 75% towed miles.
ROCKY is so much fun to drive I use it for daily errands, but my spreadsheet keeps track of all the mileage.
