Hi Jack,
the age old problem is available space and what to bring with you.
In truth there is no ideal one size fits all. All you can do if try to make use of every available space by planning your trip accordingly and what you must take with you.
I do not travel light, but we as a family have conditioned ourselves to pack for most eventualities, taking what we need to live comfortably without too much excess. if there was an ideal solution to do away with the need to carry some sort of mattress or if there were a mattress that took up next to no room and could be deployed quickly when needed and stowed just as quickly when not, I would take that option, although as with most things camping wise it’s a compromise, that needs to suit how you use the van
instead organise the available space to accommodate my my have items, so that when needed deploying and stowing are the least faff possible.
IMO less is more, although three girls don’t always agree, particularly when the van is packed and I get presented with , “Oh this needs to go in “ followed by “ and this” “and this”



We have four of us normally (upto six occasionally) and pack accordingly for each trip, depending on duration, potential weather, location and type of holiday environment we are travelling to, including potential local resources, if needed, such as laundry, shops etc.
I agree the full size comfort mattress does take up a lot of room, although if you pack correctly for the available space the comfort mattress just become part of your normal set up.
my experience over many years, various VW Vans and car camping is you will always fill the available space (and some)
SIM’s still take up valuable space as well, they are a PITA to fold up small (particularly in wet weather) and don’t provide a flat surface to place things on the rear shelf unlike the factory full size CM, which can be used to place all your soft / lightweight items, such as pillows, coats etc when travelling and whilst the down stairs bed in not made up.
(fitted / elasticated edge sheet attached to the CM even when folded, duvet cover as the upper bed sheet slide over the mattress)
”really useful“ clear boxes, with lids, are really useful!
organise your gear in the boot area. You can get these in varying sizes that allow you to maximise the height and width of the space under the multiflex whilst still being able to see and access the boxes when needed, it does take some trail and error , but you can fit an inordinate amount of gear into those boxes when packed accordingly allow say cooking / eating / plates / cutlery, washing up gear etc to be in one easily available box ready to be taken from the van as needed, with the added benefit that the gear you need for a meal time etc is all in one place & goes back in when used and cleaned which is then put back into the van out of the way.
I find the order you pack gear into the van should be the reverse of when you will need gear / frequency whilst camping
if you need to the boxes can be taken out of the van and stacked, cover with a simple lightweight tarp.
making use of the additional space, to get thing outside the van can be useful with a full complement of campers, the wind out awning can offer a huge amount of storage space when onsite, fitting a couple of simple waterproof (tent type) tarps attached to the sides of the awning arms, attached with bungee balls and pegged out at the bottom provides a serious amount of space, the tarp can be used to cover (pegged down) anything you leave outside the van. The tarps fold into a small bag and take up the space of a regular packet of crisps.
Window bags can offer a huge amount of space for clothes, when used with packing cubes, allowing a fixed place for clothes, easy to access and making use of an otherwise dead space. Four of us are able to pack all our clothes into two packing cubes each, for a two week holiday.
Keys / phones glasses / sun glasses can all be placed into / onto the bag as designed.
Technical clothing can severely reduce the amount of clothes space needed.
Shoes can be put either side of the multiflex board legs on the sloping panels when travelling and not in use. (In the Footwell or under the van when at location)
Microfibre full size towels roll up to the size of a can of coke and are a lot better than you may expect at drying off after a shower. Four of them easily fit in one under seat draw.
Beach towels can be placed on the rear seat as additional cushions.
not sure if you travel with a fridge, but this can be secured and stored behind the front seats to give more boot space And does not interfere with bed set up.
Fold flat canvas storage boxes can be placed in the footwell one at site to allow all the daily clutter, that needs to be accessed periodically, can help a lot with the tidiness of the van whilst camping.
Hook up cable etc, can be placed in the space in-front of the starter battery (engine bay) as can 1 litre of oil.
Car tidy pockets, the type that normally strap to the side of the chairs / headrest and sit on the unused part of the seat are great for hanging from the two interior coat hooks which can provide a convenient place to store phones and small items such as keys , wallet and anything else you need to access know exactly where you put it.
use the available space in the camping chair void between the folded up chair, an amazing amount of soft items can be stored.
have fun playing with your set up and let us know if you achieve the perfect set up and solution to the mattress issue.