[Amps] Holes vs. screen for chassis ventilation?

[Dan Levin]

Am building an HF amp, and will need several large (~3" diameter)
openings in the chassis for ventilation.  I would like the chassis to
be as RF tight as is reasonably possible, so trying to figure out the
best strategy for shielding the openings.

The two obvious options are to use a pattern of (small, say 1/4")
holes, or to cut a big hole and then cover it with (presumably)
aluminum window screen mesh or similar.

I've searched for answers, but all I found was some general stuff that
suggested that smaller holes were better, and to keep holes under
lambda/30 if possible.  My guess is that fine grid aluminum mesh (as
in window mesh) would do better than holes - but since I am having
Protocase build my chassis, patterns of small holes are actually
easier for me to implement (since they can cut those, but I have to
deal with the screen myself).

Anyone have either a) answers or b) pointers to good sources?

Thanks!

                                     ***dan