If you are using a 10 MHz square wave source the 50MHz component is already there, just filter and amplify it, no diodes needed. This is what i do for my other pluto where the 50MHZ was only 14dB down on the fundamenta (just not quite enough to just filter and use)l The 20 and 40MHz are much lower (>40db down)
The multiplier building and surgery on the pluto was the easy bit (around an hour) Persuading the pluto that it had a 50MHz reference AND getting it to remember it had a 50MHz at power up, took 6 hours visiting a number of "non-solutions"!