Transporting a 150 mm (6 inch) telescope

New member/total beginner here - I have a question about transporting my 6 inch Bresser Messier Dobson. Since I plan on visiting a few islands, there will be lots of driving and ferry rides involved, so I’m looking for any advice on how to protect it from the Sun and the heat as much as possible. I’ve already started my travels, secured the tube in the back seats with seatbelts, put towels around it and covered it with a sheet and a silver windshield sun shade (I don’t have a telescope bag). I used the dust caps/covers that I got with the telescope to cover the aperture and the focuser (the aperture dust cap is a sturdy, black plastic cap with no openings). Everything seems to be okay so far, but I wonder if there’s anything else I can/should use to protect it from any possible direct Sunlight entering the tube (is the dust cap enough) and to keep it as cool as possible in the summer heat.