Rich, unless you are talking about doing something like the length of a ship kit hull,,,,,,I have the perfect "cut off wheel" idea for you
go to UMM-USA and look at their razor saw
one of the "tricks of the trade" in modeling is "slow and controlled",,,,,,,the UMM saw lets you do that, costs about the same as a set of Dremel wheels,,,,,,,and gives you that little "stop, hold it, am I screwing this up?" moment,,,,,,,the wheel just goess whiiiirrrrrrrrrrrrr, PING!!,,,,,and then you don't have to ask, lol
http://umm-usa.com/onlinestore/product_info.php?products_id=35&osCsid=d54ca90b52077525368e11ffce18e3ef
each blade has two teeth pitches, and you can mount the blade for "push or draw" use
it's fine enough and controllable enough to be able to lay it right along one of those casting blocks that's bigger than the part (we've all seen those), and just slice right off, always in control,,,,,,,it's what I use to cut noses off two planes to change their versions
Rex