Cheers, I've done it on a Nomad and a few MegaDrive 2's before without any problems - and I've done your mod to change the MegaJet to English from Japanese which works fine.
For the 50/60Hz mod I normally just lift the pin of the chip and switch it, so I'll have another look at the MegaJet and see if I can trace it to any jumpers instead.
Thanks.

And yes, I know I should just dump my one and only PAL game which refuses to run! (Castlevania) <_<