I think of their life cycle in terms of quarters. Take the time you will grow them and split it into four equal numbers of days. Adjust protein levels based on what quarter it is :1st quarter is 28%, 2nd is 24%, 3rd is 22%, 4th is 18%. The most you could shorten that to is probably about 18-20 days per quarter, but you might be able to do something like that and get a decent conversion ratio and a bird that is well filled out, but on the smaller side.
Midget whites could be an option as well.
I have raised some BBW that were less than 10 pounds after 16 weeks, but not many.