On the hot-side ?? (temperature)

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I'm a bit concerned about heat generated from my (new) SCA rack - currently housing 8 N72s.
I notice that after and hour or so they top is quite hot - particularly over the power supply area, but also over the modules - not too hot to touch, but certainly as hot or hotter than say, some of the tube comps and other pres here (Neve, Quad Eight, Thermionic Culture, Retro).
The unit is set up on a couple of small blocks to allow some cross venting, currently just sitting in the open, on top of a cabinet.
Am i just worry wort-ing?
Do they generally just run on the hot-side?

Thanks anyone, they sure sound great... would be a real shame to fry 'em!

Scott