Laurenth , here are a couple of threads where we kicked this issue around pretty extensively; kind of the 'Zombie Thread'. For framing the issue a bit, The US available Panasports use a conical shaped attachment point, and the UK based Minilites use the curved insert you have. This issue also concerned me, particularly when I pulled off the highway two years ago on the way to Las Vegas due to excessive vibration. I discovered one of my rear Minilites was loose enough that it was going to depart the car!
You can see in the threads I contacted our NA Minilite supplier and had him inquire. They said the design is OK, but no real details were provided. I also considered machining my inserts or getting something made up.
lotus-suspension-f42/alloy-wheel-collar-needed-t25785.htmllotus-suspension-f42/minilites-panasports-t25995.htmlI ended up sticking with the supplied curved inserts. I also bought an excellent Nader Nut wrench from a poster here and a solid steel handle to make sure I have the nuts/spinners sufficiently snugged down. I was using a flat steel octagonal wrench when I had the wheel issue; it would start to bend before I was fully torqued. Similar tools with torque wrench handles are available for spinners.
tool-talk-f43/octagonal-spinner-tool-t27627.htmlbusiness-listings-f3/knockoff-socket-wrench-t2268.htmlNo issues since with roughly 11,000 miles including two track days, so I am cool with them as is now.
Curious what Andy at Spyder might say; maybe he can provide torquing recommendations?
HTH