I've implemented the main changes so that I can get a 3D print to confirm, but I haven't yet thought about battery or speaker placement. So that I can still fit in the 230mm target, I've aligned all Tetrinsics. The reason why I've gone with 18.75mm spacing is because the previous attempt was 19.7mm spacing and I wanted to see if I could overshoot the spacing required, and I thought that a 0.75mm gap was achievable.

[16 July: Edit 1] I've printed out the concept and it's more or less got acceptable spacing. I'm going to try for 0.6mm spacing between Tetrinsics (so an overal pitch of 18.6mm), partially because there's a lot of measurements that are intiger divisible by 0.6 (e.g. 1.2mm aluminium skeleton frame, 18mm width, 63mm active length).