A while back I bought one of these for the grand rocketeers - $1.50 at Michael's. It is a rocket shaped Mylar balloon. The fins are held on with 2-sided tape. I glides pretty well and is indoor safe (i.e. light). On the drive home the gears spun up to speed and I decided I wanted one for my own devices.
When I got mine, it was on sale half off. I fashioned a card stock and foam board mount with a 24mm motor hole. This slides on the back end and holds the fins. The thing is so light that this extra weight brings the CG to almost the middle of said motor mount assembly. Per Rocksim, I needed about 2.5 oz to get it stable. To this end, I poured lead shot along strips of duct tape, folded them over and taped them to the front. The resulting 42" long, 4.5" diameter rocket comes in at about 5 oz unloaded.
This real time build is not iffy. I wanted to fly this on a mild D5 but it it a tad heavy and draggy. I'm worried the the Mylar body will buckle under even a D12. Then it is now nose heavy enough to lawn dart. I may yet try the D5 and see what happens. It will fly off a high power pad.