I used that same primer and paint setup you used....i only cured it leaving it in the sun (did the job in the summer), then running the sled in the winter....from what i can remember i never had bubbles at all.
its been 1500 miles and i wish i could check it but im at school. if i remember correctly a little rust started to come back at the y pipe....ill try to get pics next time im home with the sled out.
Ok i found this pic from last year....its near the end of the season. ill still try to get a current one.
ps. the seal between the y pipe and the actual pipe wasnt perfect at first and sprayed a little rust out from inside the pipe...