Hi Endspec -
One nice thing about using a thick frame plate is you can tap the holes in the plate and screw direct to the plate so you can eliminate nuts on the other side. Wow - that'll make life easier!

Make sure you use lock washers, use coarse threads, although in #6 and #8's I don't remember if there are coarse or fine. Also your tolerance in layout will have to be closer as you will lose the "slop" for misalignment that you get with an oversized thru hole (actually two holes - the hole in the plate and the hole in the component). A trick I use for all my layout work is to draft the plate hole layout in CAD (I use AutoCAD, but TurboCAD is free), then just superimpose a full size print on the frame plate and center punch thru the drawing. It increased my layout accuracy by at least an order of magnitude. Using the mirror plate I might also suggest doing your layout on the underside (reverse the print), drill each hole with a pilot hole from the underside, then finish drill from the mirror side. The idea is to protect that finish as much as possible. But you have plenty to practice with. Keep your tap holes smaller than the book spec rather than larger/oversize and let the tap bring it to size. That way you will have the full strength of the thread(s). Good luck with your build, show us pictures!!
Mike
If there's no sound in a vacuum, where'd the music come from..?