I have made 3 custom chassis and each time it was the wires that stuff me up. not only that make sure you decide which wires you’re going to use in the build. if it is a tight build with no need for flexibility I would go with PTFE. if you do need flexibility and you got an open type chassis then silicone is your friend.
with a crystal chamber make sure you have the wiring diagram setup first and then try to accomodate your chamber wires from the neopixel and consider how you are going to attach your neopixel to the crystal chamber and consider how those wires, remember your going to be using at least 3 wires, 2x22 awg AND 1 x 30 awg. those wires will need to go all the way to the board.
also consider how you are mounting the speaker, will it be, inhilt adapter + crystal chamber + soundboard + battery holder + speaker holder or inhilt adapter + crystal chamber + battery holder + soundboard + speaker holder.
the difference is that you will need to consider the wire lengths and the types of channels you will use and those diameters. take in consideration the type of wire as well. with ptfe you don’t want it to bend as it will put stress on the solder joints and they can come off (especially the 30 awg trust me I learnt this the hard way).
p.s. everything I learnt, though I rage quit and bought a chassis however with time, patience and $$ you’ll get there.