Thanks Evan for such good informations.
I've asked woody KZ4AK to take some measurements as he proposes to do some. We'll see. Anyway, I've adjusted the spreadsheet you can access on Dropbox, and the transmit time will be now about 2.66 hours with the same battery pack, maybe a bit low for a WE without recharging for example.
Let's confirm that and then I'll make the good compromise upon the batterie size.