Who said, you cannot put a battery, a power supply jack, three switchcraft jacks, a footswitch and a LED in a 1590a? My take on an A-B-Switch. It takes some milling, though. I add the drill template I used for this build, should anybody want to build one as well...
As tight as it gets, well done...! Great squeeze.... 8)
Super impressive planning and drilling!
Cool! I just did a similar mod to a corner yesterday. Hope it works for me...