Running a 5E3 with a step up transformer

I all, I hope that you are doing well.

Can you guys help me to clarify a couple issues with this tweed deluxe clone I built a couple years ago?

Have spent some time back and forth between EU and USA, so I installed a Mercury Magnetics to be able to use it with 220/230/240v primaries, it was all good despite the fact that it has stock B+ 380-0-380, a bit hot but singing very well.

A few months ago I came back to the USA, and didn't bother getting a new PT for 110V primary, instead I got a step up transformer to bring the voltages up to 220v as per my wiring.

So, I blowing up a NOS Sylvania 6V6 to later discover that the step up transformer kicks out 245V instead 220v as rated, my primary is not 110v but 126V... and B+ was above 400V with the plate dissipation on the 15w ball park :shock:

Please correct me if I am wrong, To tame this voltages I switch the primary tap from 220v to 240v and installed a "switchable" 25w 30 V Zener diode attached between chassis and B+ center tap.

As result I am having the following reading, how does it looks?

Mercury Magnetics FDTD 240M 380-0-380

W5Y3GT (50's)
PIN2=388V(without zener), 359V(with zener)
PIN8=388V(without zener), 362V(with zener)

6V6GT (50's)
PIN3=378V(without zener), 347V(with zener)
PIN4=344V(without zener), 319V(with zener)
PIN8=21V(without zener), 19V(with zener)
PIN3TO8=353V(without zener), 330V(with zener)
Plate dissipation 13w/38Ma (without zener), 11w/33Ma(with zener)

Is this ok?
Thanks

2 pics showing the Zener in the back, it's huge!

6V6s run better in a 5E3 with the plates around 360.

6V6s run better in a 5E3 with the plates around 360.

Thanks, forgot to mention that I use a 270ohm cathode resistor.