I share a set of 4 clocks with another friend/motorists. Unless you have more bikes, cost of buying is hardly justified. That's why we shared and soon an owner of 2 350's will use them too. My experience is: once set you don't have to sync for a long time, very long indeed. As a matter of fact when you think they're out of sync, I would advise you to look for another cause. In my experience the carbs stay synced almost forever. Honda did a good job on this, after learning lessons with the 4-cable operated carbs on the early 750 models. Last time I used the set is some 15 years ago. On a few occasions I had the carbs on the kitchen tabel (for experiments with the needles) and decided to see how accurate I could sync by hand, using a small allen key for testsliding under the little cutaway section in the front side of the slides. I adjusted, testslided, adjusted, testslided etc. Then I drank a cup of coffee and repeated it, eyes closed for maximum touch. After mounting the carbs on the bike and attaching the set I was surprised I had managed to sync within 2 cm Hg(!), well within factory specs.
Maybe - just for fun - I will build a DIY as described elsewhere, because I like the idea so much (simple fysics). Gives me also the possibility to check if the 4 clocks are still within calibration after all the hefty movements. The homemade set can never lie. No negatives: you need no figures, just visual information that fluid is at the same level. For the rest of you: share. Less is more.