seeing as you dont really know how high to build your drop in chances are you haven't build a rail/box yet either. Soooo join the build a jib cult, lots of into in there for ya.
ya transition is prob.most important cuz it u make ur lip onto the rail too steep or whatver ull lose the purpose of the rest of the setup and might as well make a step on rail
well i made one rail (pvc) and its about 2 feet high. i know its high but i am making another arouund a foot high so that it can be made into a flat down, or a frame .etc.