I use stick fast medium ca.
To center on the tube. I'll turn the blank round put a mark on the center of the knot and measure from the center to each end of the blank and make sure the distance is equal. You will need to figure out how thick you want your end caps cut equal amounts off the blank. Glue your tube in the blank with a set of calipers set the tube so it's sticking out of the blank equal amounts on each side
The other way I do it center the knot on the blank and trime the blank so it the same length as the tube. Glue the tube in the blank and use a parting tool to remove the excess blank to make room for the end caps.
I use aluminum card flashing.
I use 5 min expoxy to glue the tubes in. As far as blow ups go iv only had on come apart and I used ca to glue that tube in. Hope this makes sense
Here's a couple more