Custom Board Flattening Router Jig

I had an idea.  I made a jig for my router that sits over the board and may or may not flatten the face of the neck.

I got some angle aluminum and 3/16" pop rivets and a pop rivet gun.  I looked at the angle steel but it was not even remotely straight, and I have no good way of cutting it.  I cut the aluminum with a hacksaw, as most of the lengths were longer than the 12" my band saw can accommodate.  I made the bracket you see, minus the two inner struts parallel to the guitar neck.  A bracket that wide would be versatile - that was my reasoning.  It would be good for all kinds of flattening jobs.

It made a clean test cut, but the router dipped in the middle and the face of the test board was concave or cupped.  So I added those two inner braces, 3" apart, to keep the sag down.  Along the way, I put rivets in the wrong places, facing the wrong way, drilled them out poorly, you name it.  In addition I somehow inserted the tip of a brand new hobby knife (#11) into the meat at the heel of my thumb, and my unused 3/16" drill bit got dull already.  

Good times.

This is what the router would see, if a router had eyes and a nervous system:

I'm going to have to pick up a piece of 1"x3" or similar, find a truly flat place to stage this (maybe my dad's table saw table), and flatten at least a one-foot length.  Only then will I feel reasonably safe in trying to flatten my guitar neck.