I dunno if the synch linkage would work correctly with a downward-pointing screw - hadn't thought of that. I guess another idea would be to replace the stock synch screw with a hex head or Allen one a couple inches longer (if such screws even exist - I haven't looked). Whether pointed up or down, it seems like that would put the point of contact for the right wrench in a more accessible spot than the stock screw. Either way, this mod should happen with the carbs off the bike, so a careful bench synch could be done first. I'm not familiar with how these carbs are accessed on EX500's/GPZ500's - must be open access from above after removing the seat or some piece of bodywork. I hadn't even thought about how to access the stock synch screw before installing these carbs on my 650 - it starts and runs well, but I'd like to be able to dial in the synch really tight to minimize vibration. One of these days, gggGary is gonna try these carbs - maybe he could give this some thought aforehand. So far, the only downside to this mod that I've found is the "between the carbs" throttle cable and synch screw access.