The bungee method for the thrusters, I'd like to lay claim to this method because that's how I figured to attach mine, now I may not have been the first but I figured it out myself lol.
You'll drill holes to insert your thrusters to the jetpack, take 2 screw in hooks (like you'd hang a lamp or plant from the ceiling with) screw one into the end of each thuster insert, then just get a short bungee cord and hook it to each of the thrusters from the inside of the jet pack and viola! Done, thrusters will stay in place and still swivels and makes for easy breakdown when done.
As for the rocket , securely glue a long bolt to the bottom of the rocket, I drilled a small hole in my rocket and seated the bolt in the rocket about 1/2 inch. Drill a hole just big enough for the bolt/threaded rod on top of the jetpack where the rocket seats, use a washer and nut to screw on from the inside of the pack and done. I'll try and find the pics of my build from years back so you can see first hand. Hope it helps.
Here's the pics from my build 4 years ago, i didnt have any for the rocket, if I get the chance Ill take a few, here's the bungee thruster, I was using a big bungee rubber band thing at the time, but I think an actual bungee with the hooks on the ends works best.
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