Proof is in the pudding...Here are photos on my weigh scale of the FP 25C (1800mah) "4S" pack as well as the FP 25C (3170mah) "3S" Pack. Just wanted to cler this up, thank you.
4S (25C) FP1800mah = 185 grams with deans/heatshrink/velcro
3S (20C) FP2170mah = 178 grams with deans/heatshrink/velcro
I do stand correct my 4S are not lighter, but equal, this is however with one more entire cell on the pack though.
I do not have any 25C 3S 2170s' at the moment but know for certain they are less than 5 grams heavier than the 20C version, cheers.
So in conclusion with Deans on the AT 3S 1800mah pack you would be looking right in the 183-186 gram range, that is however with one less cell.
There is no discounting the fact that the new AT/Kong packs are a new and growing technology, however if there is one big shortfall they have its their weight imho. Weight on the 450 sized helis ia a "huge" thing when you are talking about hucking it around with some authority and control.
...Once upon a time there were Nitros, flybars and frequency pins...