What are you using on the sides and at the base against the block for a sealer? Could it be the seal holder seams leaking and seeping down from the seam at the block base or sides. Yamabond and Hondabond case sealer works great on sealing these areas.
Also try putting a dab on the seal ends while dry. These seams are pretty tight for any RTV to seal for thin synthetic oils. This is the reason these sealers are used to seal 2 stroke motor cases that never use gaskets. Raced 2 strokes for years and RTV silicone based never sealed cases . They would leak bad when using RTV. Yama-bond is thin and is painted on the surface. It does not squeeze out like RTV. Only apply a thin coat to what you want to seal.
It leaks directly at the bottom of the seal not from the sides. that's why I want to machine the aluminum seal holder to shorten it and tighten the seal clearance.