Jim, ground clearance CAN be an issue, so you'd have to be careful taking a HiLo into unimproved camping areas. You'd probably drag the axle before hitting any of the tanks though since you wouldn't be encountering curbs.
I don't think you can mount larger tires or wheels without also raising the frame over the axle. I have an old thread in this forum where I had a 1-1/2" rectangular spacer put in between the axle and the frame, which increased the space in the wheel wells. The benefit of this allowed me to mount 225 tires on 15" rims instead of the 205 OEM ones and, this lifted the frame about 2" over stock. I did this on the advice of the welding shop where I'd taken the trailer to have the axle moved, since it was mounted too far back on the frame originally.
Here's the thread where I show this modification:
My Trailer is Overloaded, Post 24. As I recall, the welding shop charged me $400 for this modification, and it was worth every penny.
- Jack