This is a interesting question because I actually have just starting jelqing for real again after hanging and manual stretching for months. The reason I started jelqing again was to increase my blood flow because my head/glans was severly beaten and my blood flow was down as a whole resulting from two much length excersizing. I would even get a little pain now and then from gripping to hard on the glans. On the plus side of focusing only on length excersizes for months I have gained about 2.5 inches in length in 5 months times!
Now that I have been jelqing for a couple days (I mean intense jelqing a couple hours a day) I have gained a little girth, my dick seems more sensitive to touch (quicker to erection), better blood flow, a little thicker and hanging a little better when flaccid. The negative side effects of jelqing though with little length work is it seems like I have lost a little bit of length just a little, and since I measure every day (multiple times a day) this data I gathered is very up to date and accurate. So based on this new knowledge, I think I am going to quit the jelqing again since my blood flow seems to be back to normal or better and continue on with the hanging and manual stretching for length on till I work up to my super goal of length gains, then its time to tackle the girth. Another thing to think about is my dick seems a little more flexible and soft when flaccid because of the jelqing, so maybe this will help with length gains from stretching and hanging.
Now that I have proven to myself and lost a little length I beleive from girth work (this may be inaccuarte since I only measured once today and it wasn’t my strongest erection, I’ll have to measure later tonight to make a final judgement), I believe the best thing to do in PE if you want length and girth is to work on length excersizes first then when blood flow goes down jelq for a few days intensely until your penis is healthy again and blood flow is back up then continue on with the length excersizes for a couple weeks or months and then repeat this cycle again by jelqing for a few days then going back to the length excersizes again. Maybe we should also overshoot our length goals by a certain margin so we can compensate for the lossage from the initial girth gains.
This is my current theory but this could change at any moment based off my future gains as my PE has in the past based on the current data I get every day, so we’ll see…