Old school alignment guys; gauge mount idea. What am I missing?

DionR said

I should have been clearer. One thing I really want to avoid is having to pop the dust cap off. And I refuse to remove the nut. I want something I can place on the wheel that doesn’t require removing parts and such.

So far I haven’t seen anyone tell me my ideas won’t work.

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I went through this whole process recently and I didn't want to remove the rallye centers either. I didn't find a design that would clamp on without spending a decent amount of time and money. The wheel alignment fixture I have is similar to the one on Amazon for $90 in the US. I bought a pair of used Hoffmann's that retail for over $3k for $150. Its handy to have 2 but you could get by with one. I didn't have time to design and fab something after the alignment shop couldn't do my alignment.