Details of bubble plates build parts?

[Bottles]

Hi all,
I'm uk based and have started to look at making 4 inch bubble plates. I've looked at various builds but missed any info on what parts people use for the bubbles and down comers.
There are suggestions of using plasma cutter nozzles, but no sizes. I'm not sure where to go to find consumables for plasma cutters to even start looking at what can work. Verses what others have found works best.
To be honest I'm not sure if I'm after a percentage of area on plates to be bubbles or the sizes of depth of down comer for depth of plate as most important.
Andrew