I ran mine tubeless also. Mine was a heavy street car that ran 9's with these tires. They NEVER leaked any air. I did prep them with a lot of soap on the interior of the tire. I poured it in and coated the entire inside. When it dried and some of the soap puddled on the bottom, I moved the soap around until it was all absorbed by the tire.
Eventually the tires got used up. Had them for years and sat in the garage over long winters without lossing air. BTW, these were also screwed to the rims.
Allan G.