Leakage at piston rod of an aileron flight control actuator (VL seal)

[rvdv]

We are experiencing difficulties in reaching a perfect sealing on piston rod of a primary flight control actuator (aileron). It is a Skydrol hydraulic system. The used seal are the VL Seal from Shamban (2 VL seal and 1 Excluder DC). The bore and rod dimensions are per AS4716 (around 34mm). The leakage (1 ... 2 drops) are coming after 1 or 2 weeks of pressurization at 30 bars (435 psi).
Since this type of seals are difficult to install we think the leakage is coming from wrong installation.

Do you have experienced such problems with these kind of seals ?
Are the AS4716 dimensions sufficient (squeezing not sufficient) ?
Is there a better seal system for piston rod (Plusseal, ...)

Thanks in advance