the fix in the Sierra is not a synthetic sleeping bag, but a decent tent to control moisture in the first place
I don't believe it can be done. My Hexamid is about as open as a tent can get and I have had it dripping with condensation.
The only real solution I can think of is to set your tent up under a low hanging tree to help block the dropping cool air but setting up under a tree is a very bad idea.
in about 100+ nights I have had "dripping" once and that was caught by the interior tent. 60% of the nights, I had maybe some moisture on the tent fly, but nowhere near dripping, usually dry in minutes after taking down the tent. The other 39.n% was dry, bone dry. Cross ventilation is the key. If the air isn't moving at all, it usually gets the slight moisture in it, but never enough to cause any concern to get moisture on your bags. This is with three people in the tent, too.
Big Agnes Copper Spur so far my dryest tent. it has vents on both gables.