theres a problem with that methods. when you buy aluminium extruded bar its bowed and twisted by nature. its put in a vise, then the slots for the rails are milled, which are flat and parallel to each other and square to the ends, but not necessarlity the rest of the plate.
then the rails bolt in, which are also reasonably flat (1 or 2 thou per foot deviation is the spec if i recall). the ends of the plate and the rails register to the uptright when it goes together.
so, the BACK of the plate is a non reference surface and is highly likely to be all over the place. so if youve clamped the back flat then bolted the square rails (which arent as stiff as the supported round ones), you may have actually made you machine worse.
overall though, were only talking a very tiny amount over the span of the router. if it fits together correctly and runs smoothly, your generally good to go and nitpicking the details isnt warranted, unless its bend by some massive amount like 1mm over 36". then theres definitely something bent.
- oh, and please tell me if im confusing you and jaydawg in some of my responses, i sometime mix up your names.