Hi
I stretch every workout, which is usually 6 days a week, twice a day (quick, easy workout in the AM, much more intense in the PM).
Noticed a big difference in flaccid stretch length after only 2 weeks or so after adding manual stretches to my routine. Was very pleased. I particularly like the various fulcrum stretches.
Right now, I like alternating: I’ll do a set of jelqing for 5 to 10 mins, then stretching for 5 or 10 mins, then jelqing again, etc. That jelq after a stretch really seems to fill things out nicely.
For me, just as Luvdadus states, it’s not possible to say what gains could be solely attributed to stretching, but I did notice (or perceived) a difference when I added the stretches.
Sorry could not be more help-