I wanted to hang some of my high power rockets on the wall in my shop, so I did a quick design in Tinkercad for 38mm, 54mm and 66mm rockets (roughly 1.6", 2.1" and 2.6"). I didn't do any structural analysis of these, but I printed with 0.2mm layer height, 3 perimeters and 50% infill. No supports are needed, but the lower screw hole might need a little cleanup. They seem plenty strong to hold up my rockets. There's some discussion about these mounts here: https://twitter.com/GrouchoDuke/status/1579552887017177089

I designed them to use 3/4" wide x 1/16" thick cork tape to help protect the rockets from scratches. I used Preson P10806, but I don't have a good store link for it. Felt tape will probably work too. Get something with a good tape on the back, so they don't peel up over time. If anyone finds a good supplier, post a comment with a link and I'll share it with everyone.

The brackets are designed to be held in place using two #8x1.5" sheet metal pan head screws drilled into wall studs (yes, I know sheet metal screws are not wood screws - they work fine). Here are the screws I used: https://www.homedepot.com/p/Everbilt-8-1-1-2-in-Phillips-Pan-Head-Sheet-Metal-Screws-25-Pack-34682/202102341

These look like they'll also work. (My affiliate link - thanks!) https://www.amazon.com/Hillman-Group-80022-Phillips-100-Pack/dp/B000BPFYS2?&linkCode=sl1&tag=grouchoduke-20&linkId=be3f8ec440bda6238f31576430c9b99e&language=en_US&ref_=as_li_ss_tl

If you can't screw into wall studs, these anchors (my favorite for around the house) should work as a substitute as long as your rockets aren't too heavy and your drywall is in good shape: https://www.homedepot.com/p/E-Z-Ancor-Stud-Solver-7-x-1-1-4-in-Zinc-Plated-Alloy-Phillips-Flat-Head-Anchors-with-Screws-20-Pack-25216/100185538

It's worth noting that these mounts don't positively hold your rockets - they don't clamp them in place. So, if you live somewhere with earthquakes, you'll need to decide how to not have rockets flying around your room the next earthquake.

I've included the sizes that worked best for me. There are two versions of the 38mm bracket, one with a 2mm extra gap in the middle and one with a 5mm extra gap. I prefer the 5mm one (especially when using 3 brackets per rocket), but maybe print a thin slice of each to see what'll work best for you. My 29mm rockets seem happy in the 38mm mount, but I might add smaller ones later - let me know if that'll help you.

When mounting them, the two screw holes are approximately 1-7/8" apart. Screw the bottom screw into a stud, then test fit the bracket and adjust the screw depth so that it's pretty tight. After that's in, use a level to align the bracket vertically and screw in the top screw. Two brackets at a standard 16" stud spacing apart seem to work well for my rockets. You may need different spacing or more brackets for your rockets.

Also, vertical spacing of 6" from start-to-start of bracket looks pretty good to me & works to keep rocket fins from banging each other. If you do that, the spacing from one bracket top screw to the next bracket top screw is 6". So, if you mark it on the wall with a tape measure, your top screw for the first bracket will be at 0" then the bottom screw at 1-7/8". Your second bracket will be at 6" and 7-7/8", and so on.