First, hold the UNI-SYN tight against the first carb throat (start at the front or the back of the engine). Make sure the clear tube is pointing straight up. Adjust the center 'dial' until the little marker in the clear tube is centred.
Go to the second carb throat and adjust the airflow until it is the same.
Repeat for all carbs, over and over, front to back, until they are all the same and the car is running smoothly.
The more often you do it, the less adjustment will be required. At least that's what I always told myself on my poor little Spitfire-6 (with triple SUs...British aftermarket manifold).:LOL:
Webers should be better behaved.
Oh, and naturally, the engine must be running (although the carb airflow should be equal in all barrels when the engine is off!):LOL:
Only thing I could add is to check the sync at idle and then move up to a higher RPM and check again. Also, take your time. The more throats you have the longer it takes.

Good luck, Ric.
I believe, on the Offy triple setup, you need to start with the center carb because of it is your main carb IIRC , and because it is a progressive setup checking at a higher rpm won't work, the center carb will be out of balance with the other two.

See Ya,
Argh! Progressives! I forgot about that.
On a progressive setup, you're looking at the later-opening carbs like multiple barrels on a 2-barrel or 4-barrel carb. In other words, think of the Offy as a 3-barrel, with the centre carb being your primary and your outer carbs being the secondaries.
You'll want minimal airflow from the outer two at idle. At some point, after the outer carbs are at part-throttle, you'll want to synch them to each other. Not that you'd be using the uni-syn then, but I think all three carbs should be at full throttle opening together (I'd check that one with the engine off!).
You'd never synch the two outers to the middle, just to eachother. At idle, you'd set the two outers to minimum airflow (they should be pretty well shut anyway, possibly some air in the idle circuits unless you block those) and tune it pretty much with the middle carb.
OOpps! Sorry, I forgot about the intake log. With the Offy each of the three are tied together. I was recalling trying to sync Webers on a type IV VW.

I would however check the outer two carbs at a higher RPM. All things being equal the velocity through each of the secondary carbs should match.

Have fun, Ric.
OK, this may be wrong, but I'm going to describe the process of balancing and adjusting the Offy triple, this is the way I always did mine and I can't remember where I got instructions to do this but it always seemed to work.

First get the engine idling approx. the correct speed, adjust the Unisync to float the ball, as was mentioned, in the middle on the center carb, then make the front and rear match (don't touch the adjuster on the Unisys, it is set only on the center carb) by adjusting your idle screws. This will cause the engine to change RPM but now that you have them balanced bring the idle back down by adjusting them evenly. keep setting and adjusting from the center carb.
Now set your linkage stops so all three carbs are wide open, remember to check that the center carb will open fully, check that both secondaries are opening the same time and make sure everything operates smoothly.

I hope this helps :)

See Ya,