I think there can be some sync issues with the framemeister, since it doesnt run at exactly 60hz when modded (but 59. something).
The Framemeister shouldn't have any problem with that, considering it takes 50Hz without a hitch. However it will output the same sync upscaled, which some TVs can take issue with and produce a slight stuttering every second or so, most noticeable in scrolling backgrounds. The same problem would occur when modding an NTSC machine to play PAL games though, as the sync produced would be a multiple of the NTSC crystal, not a real PAL sync. The problem seem extremely rare though, so far I've only seen a single complaint about it. TVs, especially European ones, seem to have no problem handling various sync from 50 to 60 and anything in between.