I’ve jelqed for almost a year. I clamped for about a month or two. (Loved it, but my schedule got screwed up!) Nothing adverse, whatsoever.
I haven’t been able to do Horse 440’s without a serious case of red dots all over my cock! DEFINATELY: do the newbie for 3 months, and then ease into 440’s. I”m convinced they are hardcore PE excercises.