I'm considering getting the full set with 52x36 chainrings, but I'm very concerned about the issues of left crank loosening. Is this still an issue and how widespread is it?

It sounds like some people have better luck when: 1) using threadlock on the pinch bolt. 2) Torquing all [pinch and preload] bolts to the upper limit of the spec. and possibly 3) Using a Shimano preload bolt.

I would be upgrading from an ancient squaretaper Dura-ace crank and bottom bracket, so I wouldn't have a spare Shimano preload bolt. But there are many aluminum ones on aliex that should work. Looks like it would be M20. Can anyone verify?

Thanks for any advice.