Hi Robert -
The original get*set*go amps that Shannon and I built used a
top plate from Front Panel Express with everything top mounted.
The panels are 13 x 9 with about 2" clearance underneath.
If you plan on using a Hammond or other pre-made chassis,
give yourself a little extra room.
Keep in mind that the gsg design requires two 6.3 volt
windings ... you can't do it with one big one.
Remember that all of the diytube boards have the unique
ability to be used as a template for drilling and punching
your chassis. You can put it in place before you solder
to it, mark a couple of mounting holes, bolt it down, mark
the rest, then do your metalwork with a perfect fit.
If you haven't seen the pix I took, check out my site
http://tmamps.com/gsg