Hello,
There has only been one problem, so far. I was working on an A77 and there was a buzzing sound coming from the input amplifier board, which is the one closest to the AC on/off assembly. It drove me nuts for several days. If I touched the cap it would buzz, if I put in an unmodified board, no problem. If I removed the cap and held it away from the board with leads attached, no noise. I finally traced it to a bad transistor. The circuit worked, but for some reason the combination of a single metal film cap and the bad transistor resulted in noise. There is a metal shield used by Revox to shield the AC path from most of the circuit boards, and I put an additional piece of shielding (per Jack Clark's recommendation) to extend the coverage further. I also replace the input/output cables with Cardas shielded coaxial. Revox sends the output cables over the top of the take up motor, seemed a bit risky to me.
Because of the relative positions of the power supply, AC assembly and the circuit boards having two 10uF caps on top of each other doesn't seem to be a problem. Especially if you consider that the original caps are all tantalum composition. I also like the result of using a .1uF in parallel with any cap I use.
I hope this is helpful.