If one wanted to add cube spawn to new substrate in a monotub right after 2nd flush of first monotub, how long into the first project should one wait until inoculating the new spawn. About 2 weeks?

alot of variables in this one,
and bulk monos are less predictable than grains.

one must consider potential losses and contams during the cycle.

assume one adds to the cycle every 2 weeks +/-.
if its a perfect crop, the cycle is fine,
but if one loses a part of the cycle one has gaps.

naturally one could do double to offset possible loss.
thats problematic for space and supply considerations,
and, theres no guarantee one wouldnt lose a much larger crop ( in stages)
if any leg of the cycle suddenly contamed or collapsed.

it sounds good to cycle bulks and monos,
in reality, unless ya have strong crop control,
its a pyramid with potential disaster.

id suggest cycle a grain grow instead,
or bulk tubs one at a time.
or risk losing the entire crop of bulks.
unless you have a pro lab, multi bulks in cycles,
run a real chance of having several subs in stages, suddenly swept by trich.

i suggest caution building up a grow like this.
the potential for collapse, pry exceeds the low cost investment ratio,