My experiments with stretch/flex are going well. I do like to theorize and then experiment. It is much like Nassim Taleb's idea of tinkering, always informed by some nascent theory and the need to test ideas.
As you know by now, the idea is to try to flex a stretched muscle or stretch a flexed one. This lengthens the muscle, a factor in speed, flexibility, and mass. It also alters the expression of proteins involved in muscle growth. What I find so nice about this technique is that my workouts are now really quite brief and I feel quite a bit more flexible with no soreness at all.