Yeah, as the guys said I wanted the whole front and rear chassis plate assembly to be removable from the frame as it makes it easier to work on. We haven't done any mods yet as we are still getting the first kits packed and demo units built. But I imagine there will be a fair amount of people hacking around with these once a few are completed.
Some suggestions for mods would be:
a Weber Ceramic Signature 8 rather than the 8S we use if one wants a brighter sound that breaks up more easily
a Jensen Mod8-20 if one wants a more rolled off sound that breaks up later.
I will say I tried both and liked the 8S much better than either.
One could vary mid scoop filters by changing resistor values. That's gonna be a whole thread unto itself, I am sure.
If Clark can ever get the time away from filling all the speaker orders he is getting I have asked him to make up a cabinet out of bamboo. That would look pretty cool, maybe with a nice leather handle. It should be possible to add extensions to the standoffs that hold the front and back panels together, allowing for a deeper cabinet frame between them. That should make it possible to use an alnico driver.
And I suppose people will do the usual putzing around with fancy wire and capacitors. If you decide to do this be sure to keep the coax wired at the input as coax or the amp will get noisy. Also the wires that connect front to rear are stranded specifically so that they can flex without stress if the cabinet is opened up a lot.
Oh yeah, one more thing - EH EF86s won't fit. They don't really work in this application and we realized they are fatter than the typical EF86, so we sized the chassis hole they poke through just small enough to keep them out of the amp. We are currently shipping with winged C 6J32Ps which seem to offer great bang for the buck. And of course one could try RFT, Amperex, Mullard, Telefunken, etc.
Another interesting aspect of this amp is its super high input impedance, 10 Megohms. This should make the decision about whether to use 250K, 500K or 1meg volume pots on your pickups a little less, uh, picky.