I dont bother with the AP crate, i use a suitcase. Weighs a good kilo or two less than the AP crate.
The Unit fits nice and snug in the case, i lay my wet suit down in the case 1st then place the lungs front down on the wetsuit. I put the mouthpiece and the scrubber can, mask, smb, Wet suit hood/boots etc inside the unit and fit the yellow cover back on. Then place my fins on top of the yellow cover & pack some clothes around the sides (t-shirts/shorts) and some basic spares (cell, batteries,scrims,orings and greese) and close the case up.
Case middle section zips out to give more depth if needed, but TBH unless you put lots of clothes etc in as well you dont have to bother extending it.
Ready to go
on my last trip to the redsea it weighed in @ 26kg. Has an extendable handle and wheels so it easy to cart around. And most imporantly does not advertise to the world expensive dive equipment.
The Elecs and VR3 i take as hand luguage in a nice light ruck sack these weigh in at just under 3kg's. The suit case cost £39 from Cheshire Oaks (Ellesmere port, Wirral)
Tip dont pack to many toiletries as these all add up weight wise, buy them at your destination or at the airport after check in.
Most airlines give 20kg allowance standard then another 10kg extra for dive equipment if pre-booked and then 5kg hand luggage. So for me i have never found the weight to be a problem. Just dont leave you much room for clothes
Hope it helps
ATB
Gareth
P.S no need to take the 3ltr bottles, Most places that are CCR freindly (booster pump/O2/lime) offer inspo bottles for hire nowadays. Just give the dive centre you are using an email plenty of time before you depart and they will make sure they are there for your arrival.