I noticed in one of the links some extreme heresy in the form of curved beams. I can see how they claim that such beams don't over-stress 2-stud fittings, but it looks to me that 3-stud fittings must involve some serious bending and friction problems and you are going to have to use multi-grips to remove them.

I can understand aluminium though - I had the Auto Chassis 8860 from 1980 and one of the wheel hubs shattered during a... er... speed run down our very steep driveway. The kit was never the same with only three wheels, and I learned that trikes and motorcycle sidecars are inherently unstable no matter what your maths teacher might say about the stability of tripods. A tripod might be stable, but a moving tripod is an accident looking for a place to happen. I still have the cool shock-absorber parts though, which make for cool starship landing struts or mecha legs.