Sorry, but you have absolutely no idea what you are talking about. I have a few snake books and they can grow up to 2.5 m normally with some being seen at 3m. I go and catch snakes regularly at work. It is definately not the norm but they do exist and generally stay away from people. Generally the ones we catch are under 2ft. Most often juvenilles. It is rare to actually encounter and adult. Last King Brown I saw over 8 ft was in Feb at around 2100 pm and was minimum 8ft and I know this because I parked the Nissan utealongside it to gauge its length. The reason most people dont see them is generally King Browns are nocturnal and depending on time of year can be diurnal.
Also come down to the South of WA 6ft plus Tigers are very common.
If Australia Zoo reckon they dont exist then they need to get out our way a bit more and consult some snake experts that have confirmed evidence of snakes this big.
If you want to call me a liar fine, but on most occassions I have had other witnesses.
Olive Pythons are known to get over 6.5m.
Australia Zoo by the sound of it actually know very little, Maybe consult a couple of experts like Steve Wilson or Gerry Swan who are experts in the field. I can name a few more that can verify snakes this size.
If you want to confirm sizes contact your state museum reptile experts.

