I'm going to vent our new range hood directly through the roof. Since i still have the complete kitchen opened up, including the ceiling, I think it would be easier to do it know since I have easy access to everything. My concern is with how exact I need to be with the placement of the hole. Since the cabinets and stove are not installed yet, how accurate must I be in the measurements. I pretty much know where the hole needs to be, but if I'm off an inch or 2 left/right or front/back will I be setting myself up for problems since I'll be using rigid duct work?