I have Scangauge 2 and watch my instant MPG from time to time. I noticed that on take off from stop my gauge shows me instant MPG readings in low single digit number (sometimes 2-3 MPG) for a first second or two. Do you guys all have the same gauge behavior in your HAH?

High power demands + low speed = low MPG. Perfectly normal, and just basic physics.

We are not talking about physics here. We are talking about some particular observations.
So no one HAH owner has Scangauge?

Dude - ScanGauge (and the built-in trip meters, and OBDII scanners) derive MPG by measuring injector pulse width, engine RPM, and road speed, along with car model, where they get the injector flow rates. These numbers come from monitoring the data stream from the OBD port that car's ECU feeds. Low road speed, high RPM, and wide pulse width = very low MPG. Perfectly normal, and any "instant" computation will give you the same number, because they all derive it the same way.

I would correct you on your statement. Scangauge uses not injector pulse width but rather MAF sensor reading for computation of MPG. This is because air consumption has practically fixed ratio to fuel consumption. The MAF reading is more universal across different cars then injector pulse information. The built-in trip computer uses most likely injector pulse with for computation of MPG.
But it is all irrelevant to my original question.

I even have the exact same behavior from my HCHII and I only have a 1.3L engine, so I would say it's pretty normal for start-off MPG to be in the single digits till you get to 10 mph or so.. maybe a higher speed in an HAH than a HCH though, due to the more than double sized gas engine.

The only car worth owning is the one that will get you to where you are going every time you need it.