The entire point of open source bazaars is they kickass on
large cathedrals[1].
Open source is not just about source code being shared. It is a gift culture of sharing[2].
[1]
http://www.catb.org/esr/writings/cathedral-bazaar/[2] The Bibles about open source from Eric Raymond (the man who invented the term open source), specifically
the Magic Cauldron.
Cathedrals and bazaars are mutually supportive, not antagonistic. Each is well suited for its respective purposes in a positive-sum economy.
One interesting thing about the myth of Ceridwen's magic cauldron is its synchronicity with the peddler's iron cauldron in the stone soup fable.
http://www.nahee.com/spanky/www/fractint/stone_soup.html(Fractint had an enormous influence on little iCEBREAKER, years before Raymond's allegedly seminal essays.

)
Even assuming the iron cauldron is an example of an
Inverse Commons, I don't see how it logically supports the position that
large cathedrals are mutual supportive of bazaars in sense that the larger and fewer they are the more supportative?
I do see how inverse commons can be shared by those cathedrals which are competing, e.g. IBM funding some open source project, but the more decentralized and finer grained those cathedrals, the faster will be the innovation.
Good call on identifying stone soup as the produce of an inverse commons.
I find 'large Cathedral' to be a redundant phrase. A 'small Cathedral' is a church, just as a 'small bazaar' is a shop

I guess you mean 'large' to indicate the 'too big' size where marginal return to growth turns negative and parasitic on its cohorts in the bazaar.
Unless the King interferes, the cathedral and bazaar compete for resources which are awarded by the market on the basis of merit. Thus functions are divided (and granularity optimized) efficiently in a self-regulating manner dictated by consumer feedback.
EG, if the waiting list to get married in Las Vegas at St Bridget's is too long, people will go to the drive-through chapel instead. If Harvard is too expensive, a family can enroll little Sally and Johnny in online classes, and so on.