Well I already have a donor roof off of a dodge caravan... I was thinking I would cut the roof about 2-3 inches bigger than my pattern that way I have a little wiggle room as far as moving it around... I am unable to trace from the inside... the side wood will be in the way.. of course that means a lot more cutting and trimming better buy a few more cut off wheels... I hate useing them since I seem to be allergic to them...