Occupancy of air distribution box?

Hello,

we want to expand our air distribution boxes for supply and exhaust air by 1-2 pipes. We currently have such distribution boxes designed for 10 connections (I believe). Since the box actually has 20 connections, we are considering only taking a few additional nozzles and then using, for example, 12 connections per box. Is there anything speaking against that? We do not want to buy new distribution boxes as they are not particularly inexpensive.

What do you think?

No problem, but it has to be re-measured as a complete system ;)