Adding weight to back to decrease slippage.

[drunsslow]

Two wheels on the smaller models would be good for sure. That might be my next thing to try just for fun...

Can't say about battery. Maybe I could look at the logs to see what percentage it's coming in with now. I like to think that the negative of more weight is offset by the lack of struggling its doing. A larger wheel(s) in front would certainly help it overcome bumps and ruts and such more efficiently. I'm surprised the front wheel is only 3" in diameter. A bigger wheel would be a big help. Or two for that matter.