We travel alot, either with the TI on the roof (when we have our camper in tow), or on our modified harbor freight trailer (yea it works but it's a POS), especially in salt water (where we go mostly).
We also have limited storage in the vehicle so I typically throw everything that I can into the boat, pfd's, coolers, masks/fin bags, etc. However I have 3 sails on masts that pretty much cover the boat and trap everything underneath.
I also have super heavy duty spray skirts that I fold over the bow when transporting, the spray skirts trap all my rigging, sails and ropes, etc so they are somwhat protected from the wind. BTW I have shredded several sets of spray skirts on the highway so be careful there.
Haven't really lost anything just make sure it's all protected from the road wind, putting a twist in your 1" wide straps prevents them from vibrating.