Choose wisely
Bob ? I have been holding off doing the wing tips until such time as the glass work for the canopy is being done, so can?t offer personal experience here. Will say ProSeal is truly tenacious stuff, flexible to a degree after full cure and paintable.
That said, should you choose to use a product other than ProSeal aside from having good adhesion, it should be paintable and not corrosive to the aluminum. I would avoid a true silicone. Some formulations of silicone sealants miss both marks ? think silicone calking with the ammonia smell. Typically, paint and silicone's don?t play well together.