In `07 and `08, I did this with a couple of different modified Monkeybone Vac Hangers as all-night-stretchers. (be VERY careful to slowly work up to a system and setup you can trust while asleep .. or else Do Not Do This.)
It was great, obviously, for continuous post-exercise
traction for length gains ... but doing that much of it (5 or 6 straight hours essentially every night that a GF didn't stay over) also lowered my erection angle (as seen from, say, the right side) from its original 1:00 O'Clock to more like 2:30. Might not sound like a lot ("l.o.t.", no pun intended) but if I had it to do over again I'd probably figure out different anchor points to attach to which could provide higher pull angles more in-line with the natural erection angle.
Additional thought, for a few bucks you can get a handheld hooked scale used for fishing (for weighing Caught fish) to see how much force any particular strap and attachment distance is providing to the dick. I never got around to doing that but guessed the forces I was using were between five and eight pounds. (Not much for day hanging, .. quite a bit for
ANS.)
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edit -- some of my words were auto-hotlinked to products. I'm sure those are top-end devices, but are not the ones described in my post.