Tango Down Stubby, one side is flat (with TGD web addy near bottom) while the oposite side has a small flair on the bottom.  

I am a right hand shooter grasping the VFG with my support hand.  Which side of the TGD stubby should contact my left palm, the flat or the flair?

I used the flair side (Right Handed Shooter). Thought of it as a palm swell.

Mine is set up to flare out on my reaction hand side. The way I use it though I doubt it would make a difference.

Wow, I thought the TGD stubby was popular.  From the response, not many must use one (or care on which way to install).

I don't grip the VFG so much as use it as a reference point for a more conventional grip.  I grip the handguard forward of the grip and pull back into it.  I like the uniformity and it it at least feels like it gives me more positive control and makes it easier to really pull the gun back into my shoulder without having to overgrip the handguard.  Some people grip behind and push into it.  Some grab the grip itself, but personally (and just personally), that isn't as stable for me.

Thus for my application (or if you think you might, in some circumstances use a more conventional grip), the priority is mounting the TD VFG so that the throw lever doesn't dig into you when you take a conventional grip and snug your hand up against the VFG.  Thus for me, my TD is mounted with the throw lever on the strong hand side, opposite the hand that is gripping the handguard.

Not your question exactly, but that's my .02.

Same way I use it.