Curious why you chose to spend $2.06 on the tubing stateside? That's a lot of money for packaging, and then to have to assemble the kits together. I'd try and get as much done in China as possible, especially the tubing, which would run you far less and you would be shipping a finished product and minimizing costs a ton.
Happy to help anyone who needs guidance on sourcing and manufacturing in China. I've become pretty savvy over the years.