stuart noble wrote:

It will cure *eventually* with *any* amount of catalyst, providing this
is *evenly* distributed through the resin. That's my experience anyway,
and I have never had reason to doubt the strength of the cured resin.
Too much hardener, however, is known to weaken the end result.

That's not my experience. I have mixed up test batches of filer with
varying amounts of catalyst. When the quantity of catalyst is below 30%
of the manufacturer's recommendation the filler never sets properly and
remains "cheesy" in consistency. It's best to stick to the recommended
ratios.