My HLT is a 30 litre URN, that has a lid that I keep on it. Helps maintain the temp and gets it up to temp quicker.
Sounds like your HLT will be like my boiler.
For that I use a large enamel tray (like a big drinks tray) for my coverted keg boiler.
But I only need a lid until it comes to the boil, then no lid required (otherwise big boilover).
yep i use a lid on the h.l.t.it must help conserve some gas i would think and save time on heating up.
with the boil i only cover the kettle untill it starts to boil then you have to let everything get out not fall back in.
i use the same as linz,stock pot lids.
i have a glass one for the kettle.