I use saddle (or cradle type) mounts that attach and are easily removable on the Tesla Model 3 Roof Rack. I keep cockpit covers on to reduce wind drag. I would estimate total range of about 225 mi the way I like to keep a safe cushion of charge. I base this estimate on driving 65 mph highway, averaging 270 Wh/mi, starting with a 90% charge, and stopping to Supercharge with around 10% charge remaining. I'm still learning how to manage range and err on the conservative side!
I see you are in Maine. We plan on spending some time near Wells starting Aug 2nd. Look for my Blue M3 with two tsunamis on top!