Well I can vouch for Imron holding up well. When my father was restoring the Shadow in the late '70's that's what he painted the cases with, and it's still there. But be careful with it. Not long after painting the cases and gas tank with the stuff, he used Imron to paint my '72 VW Beetle. He was only using a dust mask and not a proper charcoal filter mask. He then took the dust mask off because it interfered with his glasses, causing them to fog. Nearly poisoned his self. Spent the night vomiting his guts out. Had my mother so worried she called the poison control center whose only answer was give him lots of milk to drink and take him to the emergency room if it gets worse. He wouldn't go. I suspect it was the primary cause for his pulmonary fibrosis 17 years later.
Imron is a good finish, it is a tough finish that holds up very well and goes on easy. But heed the cautions that come with it.
Steven