First if possible I would move the On/Off switch so it is not so close to the Biggest tube. while I have not burnt a finger yet the potential is there

Second, that same central Big Tube does not fully seat as tube's base hits the mounting screws on the receiver. I took a thick towel and moved the tube back and forth while playing music and there was no impact, but it seems it "should" be firmly seated ?????

Neither one of these things seem to be significant nor important to the performance of the amp , just quirks of the design

Enjoy the Music