I have my Aerotech G-Force to build, which awesomely uses the same body tubes, coupler, and nosecone as the MercuryEngineeringIntegrator. I have a spare set of fins from my Mercury Engineering Integrator too that James at RocketyWorks made upgrades for. These fins are a design he originally came up with but then made improvements but cut these and sent them. I didn't think they would hold up well so he cut the better design he had, he was just so busy he forgot he made upgrades. It wasn't a big deal. I offered to pay but he sent them, I used the other set on the Integrator like intended. I like the plastic fins but they don't see to be very tough for high power butnsomenday they work fine. I could use the spare set I was sent, or get some material and make new ones in the shape of the plastic ones the G-Force comes with, in 1/4" too. My 4" and larger diameter rockets over 4 feet long will have 1/4" minimum fin sizes going forward. These may be ok because the the length isn't that long, but my Integrator should probably be 1/4". Some 29mm H may be ok, but anything above those impulses and 1/8" fins that size will probably flutter bad. Even some higher H impulse would probably make them sing, lol.
I've been looking at thread and talking some seem to think fin upgrades for the G-Force would be better. I've seen a few fly, one lawn dart horribly. To the point the nosecone shoulder was on the top centering ring at the Zell Farm launch 8/19/23. He rebuilt it, and flew it again at Halifax 9/16/23 with SPAAR. First time I forget what motor but the nosecone never came out. I took the motor out the charge went off, but the foil in the motor tube they give you blocked the charge he/we thought and it came in hot. Of course that one I missed and have no video or pictures. I was busy trying to get my Olympus(RIP)down from a tree.