just get motrbike tubes. fatter and take low pressures better . also have threaded valve stemms ,so are easier to inflate

Maxxis Downhill 26x2.5/2.7 are fine. I use them in my Surly 4.0 tires.

Here is the result of my efforts this is the first one done so far with land yachts easypeasy method
5kg all up weight

You are right I used alloy bearing housings made from scaffold tube This system has been used for some time here with no failures that I am aware of
I used the spoke design that has been Ok as well the same as my old skinny wheels 10 x15mm polyurethane foam covered with a top hat of
carbon and glass fibre 5 spokes instead of 4 last time
I have used up all the carbon I managed to scrounge now from a local boatbuilder some years ago
I guess I should be barred from calling them landy's easypeasy wheels I did use your method for the rims and discs though
Your idea of using core flute for backing worked a treat no wonder it is so hard to glue
The 21 inch motorbike tubes fit well and should be bullet proof and yes they are cheaper and have better valve stems too

I don't know how many hours per wheel I haven't kept count The answer would probably be too scary
I am happy with the result so far but I have a few ideas for streamlining both the time to build and the weight
I may try them out on a 20 inch front wheel but I need to test these wheels first Hopefully in the next week or two
The changes will be in the rim area I am happy with the bearing housings ,hubs ,discs and spokes
Will let you know if it seems like a worthwhile thing to do
Hiko

Bit more info on how I made mine Hiko

www.seabreeze.com.au/forums/Land-Yacht-Sailing/Construction/My-New-26-Carbon-Fiber-Land-Yacht-Wheel-Video/#1244482

Yes there were 5 to position the rims but a full strip the way Aus 230 did his seems necessary in hindsight
The epoxy /Aluminium bond wasn't good enough in my case I thought I had prepared it well ,coarse sanding the surfaces and acetone cleaning etc just before bonding
Oh well lesson learned so not all bad
cheers
Hiko