For me the key here is what is meant by "imprisoning." If we mean to put into a prison; confine in a prison or jail as a punitive measure without consideration for market alternatives, my answer is close to all of them. Freedom of association unhampered would allow for people-who-want-nice-things to experiment on what conditions create that best when they are given complete freedom of association.

If the crimes were ones with actual victims/claimants (govt/ "common good" excluded), prison labor could benefit the prisoner, the victim, and the prison shareholders by developing prisoner's human capital. Even obstinate or unable to work prisoners could provide value by being subject to medical experiments or worse, mechanical turk tasks. In such a scenario, less than Blackstone's ratio seems livable, as there would be an actual proportionality imposed by case law and the market.

depends a lot on the state of society.

sometimes the only way to get one's society back on track is to cast a wide net

@jim it also depends on the crimes as well as what guilty or not guilty means. I think most people's mind wants to jump straight to arresting a totally unrelated person for something clear-cut like murder which is quite awful. But we also might have cases like a very complex tax-evasion scheme that might or might not be tax fraud and similar white collar crimes. We could also have a member of a violent gang and it's unclear if this particular gang member just signaled when cops were approaching a spot where drugs were traded or if they murdered opposing gang members or store keepers not paying protection money. Acceptable numbers would be totally different for these cases.