There is no "master" carb on those style carbs. On PD style carbs (77-78) #2 is the master. On your set, the "master" can be any carb you want it to be.
Now, if you are synced well and have range of adjustment from the correct position in relation to the idle set screw, then it's not that big a deal what you're showing. If you look at the lifter arms they are often bent down or up which is basically what can cause the variation. They get bent in, out, side to side, sometimes they touch each other in the middle and bind a little bit. They are not an exact part, but they don't have to be, because it's adjusted with the individual adjusters.
Really the fool proof way to do this is (and I've been meaning to make a video of it for the longest time): We'll use a 1/8" drill bit for the example tool from airbox side. Get all the slides off "the deck" that way nothing will bind and throw everything else off. Designate #2 the master. Back off the idle screw so it's not making contact. Now get the nut on #2 to where it has about the normal amount of threads showing like you want on your picture on the right (3-4 threads, 4 is good). Now here's where the foolproof part comes in: You have only set where you know the threads at the top are a perfectly acceptable honda factory level. None of the other slides are BELOW the level of #2 (which would mess this up). Now, adjust #2 with the IDLE SET SCREW with your drill bit (just close). Verify range of motion IN and OUT with the idle adjust screw (should be making contact with the stop when turning in and out for providing a reasonable range of adjustment). Next, fine adjust #2 with your drill bit (or whatever). Now you are going to have for sure the sync set IN RELATION to the idle screw. In other words, you're not going to get them all synced to each other only to find when you adjust the idle screw it's not even touching and you have no adjustment! Now all you have to do is set the rest to the same level as #2 (adjust each with the individual adjuster, you don't need to really mess with the main idle adjust now). Easy!
