I've used two different brands for 38mm and one for 54mm. They do work, but don't expect them to last terribly long. In 38mm I've used both the ones mentioned above from Additive (bought through WM), and the 'Mayhem Rocketry' ones AMW used to sell (don't see them listed now). I did more than a dozen flights on the Mayhem ones, though I did have one break when it hit the ground, and one that didn't cleanly come off the rocket and rode it part-way to apogee (never found that half, and really hurt the altitude of that flight, obviously), and one where the 3D print deformed in the heat of my car before I ever got to fly it (I think some of the early ones were just PLA, later ones some higher-temp material). I also have a single 54mm Mayhem that has flown over a dozen times successfully so far, no issues there (knocks on wood).
Unfortunately, my first flight with the Additive 38mm one didn't go well, it came off fine, but when it hit the ground (Black Rock playa) all 3 rods bent and one of the printed parts broke where it captures the hinge rod. So I only got one flight out of that one. Since I have a 3D printer I've decided to play with my own guides similar to that design (I don't plan on making it for anyone other than me), trying to determine the best rod size/material to use for durability (or ease of replacement if I just assume they're going to bend every flight), and in a future design tweak I'm planning to have a place to capture either a small parachute or streamer, to hopefully both soften the landing and make it a bit easier to spot on the field, as sometimes I've had to spend 10+ minutes trying to find where the guide landed after a flight (of course you're watching the rocket go up, not where the rail guide came down, and they can spring surprisingly far away from the launch rail in seemingly any direction). I've had one successful flight on each size of my own so far, though one the rods bent and the other the printed part broke at what's clearly a weak point in my original design.
Something to consider, I also sharpie'd my name & cell number inside all of my guides after the first one 'flew away', in case I failed to find it but someone else did.
On the one that stuck to the rocket, at first I was shoring-up the inside of the guide with blue tape to make it a snug fit on the rocket (so you could move the rocket up/down the rail and have the guide stay in the same spot of the rocket), and I guess the tape wound up sticking on both sides. I started using extra rubber bands (another part of the Mayhem design that doesn't last long, but easy to replace) looped long-ways around the guides (and possibly twisted for extra thickness) instead of tape. The Additive one I got came with some cork tape for this purpose which seemed to work well, so after that I bought some cork tape from Amazon and started using it with both size Mayhem guides with no further sticking issues there.
