Do trays/platforms exist to mount a PC out in the open?

[frogboy]

I was wondering why people who overclock don't mount their systems out in the open on something, surely this is the ultimate cooling solution.

Therefore why are there no dedicated trays to do this? Is it a health hazard?

I don't overclock but it would be great for easy access, few fans etc.

I have something like a clear acrylic base in mind..