How To Question... Need Help

[rebelfox1985]

I am new to the truck building hobby and am in need of some help. I recently purchased the king hauler and i want to chop the sleeper to make it a true flat top. What do i use to cut the plastic with. i have seen some pics of one that was chopped and the cut lines looked like a perfectly straight cut. I used an x-acto razor saw and to be honest my lines no matter how hard i tried was far from straight... Any info will be greatly appreciated and maybe some one that reads this has some photo's or a site that explain's the complete process.