Your luggage is probably heavier than the guitar. Why not put the guitar on your back and wheel the other stuff?

I've just taken my rucksack, day pack and cobza/koboz by bus and train from Newtongrange (outside Edinburgh) to Csikszereda in Transylvania - I'm going to Gyimes, a bit further east, at the weekend. A koboz is like an obese mandola: picture on my cobza page.

The koboz is in a homemade semirigid case (karrimat foam sandwiched in fabric), which I didn't think was strong enough for a bus hold so I put it inside a wheeled holdall with a sheet of that two-ply polycarbonate greenhouse material to protect the soundboard a bit more and padding added with clothes. I've found it easier to transfer more of the weight to the holdall when walking any distance (like several miles across Budapest).