What Effect Does Kegels Have On Stretches

What effect would doing kegels whilst holding a stretch have, if any?

None.

Well, you can feel an increase of tension on the ligs when you kegel especially when stretching upward (depending on your LOT).

I think kegels while held at constant length in an extender adds tension, but I don’t know if this can lead to better results.

If you are pulling up the tension is likely to terminate in the fascia around the root of the penis, I doubt you’ll be hitting the suspensory or fundiform ligaments much if at all. In that kind of stretch kegeling can pull back the penis but it can’t increase the tension. In fact it’s probably best to relax the BC muscle entirely.