Thanks for the analysis and effort Tepples!
I don't see any good reason to restrict ourselves to 4mbit. We surpassed that threshold with the submitted entries, and all submissions are more than worthy of inclusion on the cartridge. It does cost us a few more dollars in hardware and fine pitched assembly, but it's still well within the budget.
I had the same late March deadline in mind for submissions to have any last min changes and polishing. In reality there probably will be a bit more time for changes bug/fixes before cartridge assembly starts. But March 31st is a good date we can plan to stick with annually so we can always tell devs how much time they have remaining. Anything past that date can't be promised, and it's probably time to start working on next year's compo entry anyway!

How we decide to address printed materials will have a bigger bearing on when cartridges will be able to start production. Specifically if we choose traditional cardboard boxes again which I'm unable to print myself in house. It'll easily take 1-2months to get traditional boxes printed off and in my hands once artwork is finalized. And we effectively need the cartridge rom in release candidate status with final title lineup before artwork can be finalized. For this reason March 31st deadline for rom submissions also makes sense. The alternative to large initial investment and long lead time of traditional boxes is to utilize bitboxes from stoneage gamer that I'm able to print the inserts for in house. Looking back on last volume, it's hard to say the traditional boxes were financially worthwhile. We've only consumed a small portion of the large volume that was printed 2 years ago. But people appreciate them, so perhaps that's good enough, we can just plan to not print as many this time. If we run out of traditional boxes we can always shift over to bitboxes and consider the traditional box limited print.
I plan on printing the cartridge labels in house. And if the manuals are relatively simple I would print them in house as well. If the manual is has more than a couple pages I'd prefer to send them to a print shop with the traditional boxes.
I expect May, and possibly part of June to be consumed by printed material production. Cartridges can be produced in that same time frame. Which means we could expect release in July perhaps. Opting for bitboxes and printing everything in house could pull that date in quite a bit if we preferred. Either way works well with my current schedule.