I've experienced leg tremors on LSD as well as AL-LAD. I've only ever tripped on 1P-LSD once, no leg shaking occurred. I really don't think that 1P-LSD has any special propensity for giving your legs the trembles. It's a lysergamide thing, at the very least. If not psychs in general.
While I'm at it, I'll also add that in my opinion, tremors experienced while tripping are a psycho-somatic thing of sorts. As we go through our lives, we accumulate quite a lot of tension and strife in our unconscious. Things like pent-up frustrations, self-image issues, various fears, residues of conflicts with other people or other ugly situations that we get involved in - all of this stuff is stored in the fabric of our bodies.
A psychedelic experience represents an opening, and these things want out. Sometimes, this can happen in a quite dramatic fashion, especially if you don't do anything about this issue in your day-to-day life - what I mean by that is practicing techniques that allow you to release these tensions while you are perfectly sober (at least from the chemical standpoint).
I'll also preemptively counter my own argument and say that all of the above is bullshit, and it's really just receptors being slapped around by the chemical, sending out electrical impulses like mischievous imps, activating muscles willy-nilly, making us shake like rag dolls in the hands of a petulant child.