The two mods to any machine that I believe are mandatory are:
A milliamp meter and a visual flow gauge.
The meter so you don’t over drive the tube ( you can’t mount it on the back of the machine. It needs to always be visible)
The flow gauge is just another piece of mind. Everything you need is less than $20 and if I had one before I would not of blown up my tube.
So for less than $40 bucks you have two great safe guards .