5AR4/GZ34/5U4/5Y3 SS conversion

Well it certainly looks different :^)
https://cursorium.co.uk/images/ssr-3.jpg
https://cursorium.co.uk/images/ssr-4.jpg

I did the opposite--albeit on a preamp. Added a massive tube regulated power supply to replace diodes!
See photo here

By doing this you've increased the voltage and removed the soft start effectively hitting the tubes with higher HT than designed before they've heated up. This can harm the tubes.

I have a thermsistor in the circuit, in fact two in parallel to slow it up even more. The Russian military EL84s in there will stand 315V and more with no problem, I have another amp that's been running them at 350V with no problem. Some commercially available amps run them way above 300V.

You know what your doing! I meant in the circuit though rather than in what the tubes can handle.