I've been doing this with my Rogue Ares phono preamp. The lid+sides is one piece of sheet metal of relatively low gauge; any disturbance and it rings like a bell -- not a good thing for a tube phono stage. Plus the weird tube cage thingy is ugly. So, off with the lid.
Meanwhile my Rogue Hera preamp chassis is machined aluminum, and works quite well to isolate the components/tubes inside, so the thick/heavy lid stays on.
And as has been said before -- DON'T tap your running, hot tubes with a fingernail, etc. Tap around them, or at most use a light touch with the soft part of finger (depending on how hot).
Meanwhile my Rogue Hera preamp chassis is machined aluminum, and works quite well to isolate the components/tubes inside, so the thick/heavy lid stays on.
And as has been said before -- DON'T tap your running, hot tubes with a fingernail, etc. Tap around them, or at most use a light touch with the soft part of finger (depending on how hot).