Originally Posted by jimmuller

That's a curious observation. The distance between the contact patch and the steering axis (measured either as trail at ground level or as a perpendicular to the axis so as to measure "flopping torque") differs by only 1cm or so for 72deg vs 74deg head angle, the larger trail being for the shallower angle. Rake reduces trail by moving the wheel forward, seemingly making the steering less floppy-over. So a shallow-angle bike essentially needs more rake, not less. Perhaps the apparent correlation is because shallower-angle bikes don't always have sufficiently greater rake. (Even so, as I said earlier, the difference is only 1cm or so. I don't think I could judge rake that accurately by eye. But then, my experience is considerably more limited than yours.)

IN retrospect, I realize there is one more factor in flop-over. The effective force of gravity on the steering axis is greater for shallower angle. Or put another way, even if the trail was zero, once the steering is turned away from straight ahead the front end of the bike necessarily drops more if the bike is leaned over. The effect would increase as you turned the steering more. Perhaps this is the difference. A shallower head angle could have a properly chosen rake but the change in front height would still be there.