Had a week of trying to get ready for WSIKF and fix a tubeless Sysmic wheel. For some reason after liquidating all my unused and extra wheels I ended up with a wheel that would not hold air. I have done the liquid seal stuff and it isn't good for high speeds, so after replacing the valve stem with no change in keeping air in the tire I decided to put a tube in it.
I have a tire change set up I got from Coolbrease that works great. Now here's the problem, the valve stem needs to be in the center of the tube like on a bicycle. Not off to one side like a car.
After a week of driving around the state and letting the tire shops show me how to make the wrong tube NOT work and what I could do in place of getting the correct tube, I have finally found a supply of tubes that fit the Sysmic wheels whether barrows or bigfoots.
I do have some cool things I picked up like Inky valves and some other things that look like the Nike swoosh for tubeless tires.

Any ways the tubes are center stem and run about 22 bucks. I bought 3 for my Bigfoots on the Sysmic wheels. Because I used one of the other guys stupid ideas on one wheel (which made the tire out of balance) the valve stem disappeared into the wheel about an inch away from the hole and now I need to poke a screwdriver on the valve stem hole to pop the tube so I can break it down so I can put the correct tube in the tire.
The PL wheels use an off set type tube which is not compatible with the Sysmic wheel. Now I can run at high speeds and not bounce down beach. I can also air them up or down.

What's the Nike thing?

Do you think the leaky wheel is porous or has porosity in the casting? Or a bead seating issue? Absolute certain it's not the tire?

I had a full set of Nanco's refunded due to a leak in the side wall on all three tires:

The hole for the valve stem is just drilled and not finished, its not the same thickness around the hole. with some sanding and some grease to soften up the rubber it will sooner or later leak. the bead is also an issue as the tire has to be filled up way to high of pressure to seat the bead thus creating issues later on.

Not had a problem with the 4" or 8" Sysmic rims and been running them tubeless for 6 years now. Midi Xl's, Beach racers and also barrows on 2.5" rims, the the rims are really true running/beautifully machined.

Fitting a tyre is pretty easy if the tyres are left in the sun to heat soak and soften up. If the day is too cool put them in your car where the sun can shine directly onto them. No tools required they will push over the rims if warm/lubed up enough. (I just slide the rims over a vertical 20mm shaft in my vice, that is wrapped with a towel to protect the clear coat on the rims from the vice, this holds them into position.)

Getting them to seat correctly you need to have lots of pure dishwashing detergent wiped round the bead surface of the rim and also the tyre. Leave the valve core out and inflate quickly with a large air supply/bigger compressor. The beads will then seat correctly. If not enough pressure is added quickly they wont be round as the beads creep onto their seats twisting the tyre bead area slightly and the tyre will hop up and down. I had one I had to reseat a couple of times to get it right and run true. (Beach racer)

I have also given them a 3 second squirt of underarm deodorant and a lit rag passed over them while laying on a soft surface (lawned area) and this instantly seats them well. (Leave the valve core out as well when doing this.)

Breaking the beads free of the rim for a tyre repair is simple too. DON'T deflate them completely.. let them down to a MEASURED (please use a gauge for safety) couple of PSI (2 or 3 PSI) and then break the bead... This slight pressure holds the side wall up and allows the pressure to be concentrated onto the bead area for removal. When one side is off, lube it well and then reinflate to 2 PSI and break the opposite bead. Both will slip off with a freshly lubed bead area quite easily. Some times an extra splash of water on the first bead helps it to be removed if it's evaporated from the warm tyre drying the bead area out.
Hope this helps.

Done all that. Nanco is a bit different in size. I was told by some others the issue with the beed on the wheel being a bit to big. I found out the tires from Europe are easy to instal as you said. Lots of dish soap works wonders on all except the nancos. For what ever reason they are just off enough to be a pain.
I found the easiest way to seat the tires is with a bit of starting fluid and a torch, and don't forget to leave the valve core out so the tire won't shrink and break the beed as it cools.

Stupid double posts