OK,....greetings all. Going to be putting in a new window into an existing wall. (no window there now). My question is this,...I havent gone inside the wall yet,...BUT the exterior of the home is T1-11, and I fear that this is the only siding,...no sheathing underneath. If this is the case,...what the heck do I flash the window to? And for that matter even attach it to? The only thing I can think of,...is to do my rough opening a bit larger?...cut my exact sized hole through the T1-11, then caulk the window up good...get it in place,...and build additional studs and framing around the window nailing flange from the inside?....I mean hmmm......it all seems pretty sketchy to me. If I get in there and have sheathing then im golden,....but I fear that wont be the case... Any thoughts here?