Well I'll check out his video. I'm sure they're built right. How much air? I don't know how to measure that, but when I compress the shocks, at least one of the four will make a squishy sound.
I use the Velcro strap, but I don't like it, don't like tape for that matter either. I dislike the strap because it flexes the chassis, so my ground clearance under the battery is lower than under the bulkheads, and means my chassis is tweaked any time there's a battery in it. I'd like to devise a little clamp style holder someday that holds the battery but doesn't directly exert any force on it, keeping everything as free as possible.