ok well not too sure if this still falls within your allowable methodology, but maybe if you want to, you could derive the cylinder into a new sheet metal part, ipt (choose import as a surface). Then just thicken the outer skin, rip it and flatten it.
when you save the file, just call it the same file name as the main part but add a postfix to the name to indicate that it is related information.
-Mark
Inventor 2014 Pro on Windows 7, 64bit
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