I'm no expert but have found the best method (for me) to prevent damaging the hoods is to remove the lever from the housing. Then the hood will slip on easily over the front of the housing (I still use some dish soap or Simple Green as a lubricant). Then you just have to stretch one side of the hood back enough to put the lever pin back through. Put your set screw back in and done. I usually wrap my bars with the mounting bands in place but the complete lever assembly off to get full tape coverage under the hoods. Anyway this method works for me, as I've never been able to stretch a hood enough to install with the levers in place. Maybe in the day when hoods were new and reasonably cheap. Hope that helps.
Jon Williams
Grants Pass Or