I'm the creator of the "Drones and Model Aircraft" SE site proposal. Aside from reaching the requirement for >100 committers with >200 reputation, we are doing very well.
Since our communities have a lot in common with all of the 3D printing I know takes place in the model aircraft and drone flying hobbies, I'm hoping to be able to convince some 3DPrinting.Meta users to commit to our proposal.
As I mention in this Area51.Meta post:
The problem arises from the fact that since this community is fairly different in scope and intended audience in comparison to most other existing SE sites, we have only been able to recruit a little less than half of the required supporters with >200 reputation across the Stack Exchange platform.