The way I teach it, of course as with all these matters, this is no more and no less than the ideal one tries to approach, the lower arm should be perpendicular to the floor. Now, what this really means is that the forearm should be dangling/hanging from the elbow down - if this what it feels like, i.e. there is no muscular tension and one can tell there's none, it doesn't matter what one's arm looks like from someone else's perspective, nor on video, nor on pics. No need to go into detail, but for physiological reasons, a human forearm that's perfectly dangling doesn't quite look like it does (usually looks lightly askew). It's not easy to feel "looseness" there as a billiards stance isn't particularly natural, nor the looseness of one's wrist that's part of all this (whereas grip, i.e. palm and fingers, is another matter), but the effort of learning to get a feel for this aspect of "stance" alone tends to make most I teach better players. Getting a feel for things is infinitely preferable to taking a set stance that is the result of a rationally conceived check list of "what one needs to do."
Greetings from Switzerland, David.
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„J'ai gâché vingt ans de mes plus belles années au billard. Si c'était à refaire, je recommencerais.“ – Roger Conti
