Great Picture! He looks happy but maybe a bit apprehensive...patience is the key. Even though it has been three times, it is still new and strange to him. Have you tried it with the bug screen closed? I have had Garrett out on the Seacycle four times so far. He will jump on with no hesitation now But he is still not relaxing much because it is new and exciting. It may take a few weeks before he relaxes and then I will too.
Just a suggestion but you may want to get you dog a pair of Doggles. I'm going to get Garrett a pair when we get our trike. As a Harley rider, I am well experienced with the importance of eye protection...them bugs hurt! Also, there is the chance of a passing car throwing a stone up and hitting him and you want to make sure his eyes are protected.
Thanks for the update. Hang in there....he will calm down and relax once it becomes "normal" activity......patience and time is all it takes.