If you have any hobby shops around swing by and see if they have a "bone saw" for styrene and plastic. It cuts through very quickly and a very fine line, less then 1mm in thickness, I use them for any straight lines on plastic then a very fine sanding block for details. Also, once you cut it the plastic may look flat in color, another trick is (using a scrap piece), hit the cut edge with a torch just a tiny bit at a time, usually brings back the gloss color pretty good.