It turns out that most helicopters have trim tabs. Many helicopter have several sets of tabs. The purpose of the tabs is to control the Vertical hop that occurs in forward flight. The hop is due to the assymitry of lift that occurs in all helicopters in forward flight. It is therefore dependent on airspeed. This is why many helicopters have multiple sets. At low airspeeds the outer tabs control. As the ship goes faster the control shifts to the inside of the blade where a second set may be.
HOVER ADJUSTMENT - Vertical vibration in a hover is a function of tracking. Using whatever means are at your disposal track the blades as closely as possible. This is done using the pitch links. After this you can put the tracking lights away. TRIM TABS HAVE NO EFFECT IN HOVER BECAUSE THERE IS NO ASSYMETRY OF LIFT.
FORWARD FLIGHT ADJUSTMENT Any further track adjustmens will be done with the trim tabs in forward flight.
I have a supply of tabs as does Safari if anybody wants a set. It takes a special and expensive glue to put them on. It also takes a special tool and dial indicator (IMAGE 2,3) to adjust them. Using the tools I can adjust them by about 0.010" on a consistent basis. Adjusting with out the tools will do more harm than good.