Yep...

You're both right. Cabosil, in small amounts, will thicken the epoxy. That's good for bonding and even some penetration. But for something cosemetic, I'd rather sand a highly "infused" mixture of epoxy and microballoons than to sand mostly epoxy with a little Cabosil.

PS>The wing saddle...
I typically make the top of the wing fairing with epoxy/microballoons. But where is contacts the wing, (the "not visible" part) I use silicone.