If you haven't noticed any limitations with the amp since you got it, I'd first ask, Why?
I've never heard of any reliability issues with Dual Rectifiers large enough to require a mod for that.
If it's to improve the sound, I'd make sure it's something variable, so you can compare it to how it sounds without the mod.
If it's for more versatility, you have to decide if you need it in the first place.
And I don't know what the % is of prospective buyers who would pass by an amp that was modded, but imho, any mod decreases its value. Unless it's by some famous amp builder, and can be documented..., I suppose.
I'd probably just leave it alone, and if it's not working for you, try something else.
Here's another thought...., suppose you do the mod, then at some point in the near future it blows a power tube or transformer. Then what?
I'd imagine you'd think it had something to do with the mod, and your electrician bassist would probably claim it didn't.
Plus, being an 'electrician', at least in the US, doesn't mean you know the first thing about modding guitar amps. 'Electrician' and 'electronics technician' are not the same thing. One wires buildings, the other works on electronic devices. They can overlap, but if an electrician per se, wanted to mod my amp, I'd ask him what does he know about amps, the same way I would, if he said he was a used car salesman. If you know what I mean.
