Thank you!!
Yes, you're correct, the lava texture has been stretched by a factor of 4 in the direction of flow and compressed 0.5 along the perpendicular to give the illusion of falling, and also to "speed up" the flow effect. The standard flow is too slow to believable for fluid in free fall. I'm finding in my next map that water works well like this, too, but even better if...
...create a waterfall by the method described for "lavafalls", but with the texture aspect ratio 6:0.5
...then add a trans33 face 1 unit in front of an opaque waterfall
...giving the trans33 face a different water texture than the main waterfall
...scale the trans33 texture up to 8 to 1
The result is fast-falling, shimmering water... or at least, relative to Q2's standard water.
I was playing bugdm10 on one of TastySpleen's servers yesterday and I saw a guy jump into one of the lavafalls quite deliberately, presumably looking for some goodies. So it gave me an idea for the waterfall in this next map. The map is not focused on this mini-secret, but it's something being worked into the overall design. I don't like maps that rely on a gimmick, but I think little things like the jump through waterfall, or the contraptions in the iD q2dm maps are very fun additions, so long as they are incorporated seemlessly, that is, that they fit the theme of the map, don't disrupt the flow, and make the map more fun to play.
Thanks for your feedback, and thank you for playing! I hope you enjoy it.