Hi, I know you originally posted this question several months ago but I wanted to chime in for anyone else with a similar question. I did exactly this with my Salvi Daphne pedal harp when I moved home from college. It was a 14 hour drive. I also moved my harp this way again in a small Uhaul trailer when I bought a house and moved out of my apartment.
I put my harp in the padded transport case. I firmly strapped my harp to my harp dolly. Then I firmly strapped my harp dolly to the tie-down points inside the front corner of the trailer (closest to the end with the trailer hitch), ratcheting the tie down straps until my harp did not shift at all when I tried shaking the dolly myself. This way, there is not really much tension on the actual harp. Yes, it’s strapped to the dolly, but the tension on the dolly is what keeps it from shifting around.
Then I put my mattress against the harp so that if anything (boxes or items of furniture) did shift during the trip, the mattress would take most of the impact. It’s important to arrange the furniture and boxes in such a way that they don’t shift or fall over during motion. Strap down any large pieces of furniture to the tie-down points with ratchet straps (not bungee cords). If there’s space for things to move, try to use moving blankets or old pillows to fill the gaps and reduce movement.
You’re going to hit pot holes and rough roads, but I think driving carefully (stopping and starting smoothly, taking the turns more slowly than normal, driving more slowly overall, etc) is a huge help. I opened the trailer and checked things at every rest stop to make sure nothing had fallen or shifted too badly, and to make sure the tie down straps were still tight.
