I'd use a minimum of 30 pounds weight. The RTV will dry lumpy otherwise and lumpy leaks very easy.
I've put on hundreds of gaskets dry and no leak for years. Clean and DRY surface is the key, 99% of time when I view others' errored work the surface is still dirty or oily. Oil and uncured RTV absolutely do not mix. ANY RTV and ATX do not mix, the little BBs come loose and if get in valve body problem city.
The gasket can easily be overtightened to leak too. The pan must be prepped by knocking pull in back out at all the bolt holes. The pulled in area at holes relieves the rest of flat between holes to leak.
I'll take a gasket and no RTV any day, although I have no trouble either way making it work.