I think that you are right to be concerned about adding more length.
First, we make a distinction here between measuring “bone pressed” (BP) and “non-bone pressed” (NBP). Non-bone pressed is where you measure along the top of the shaft from tip of your dick to the point that it meets your pelvis, or your “fat pad,” without pushing into the fat pad covering your pelvis at all. Bone pressed is where you likewise measure along the top of the shaft from the tip of your dick, but this time you press the ruler all the way into your fat pad, so that you are effectively measuring from the pubic bone.
NBP measures the visible portion of your dick, what you and women and everyone else sees. Ultimately, this is what we are concerned with. However, we focus on BP measurements during our PE activities, as this form of measurement will give a more accurate account of any gains a person makes. Our fat pads become thinner and thicker, depending on diet and exercise, etc.
So what are your BP and NBP measurements? Also, as others have asked, what is the circumference of your erect girth? Get a piece of thin string and measure it!
If you are already 8” or more non-bone pressed, then my advice would be to work on girth only, depending on what your present girth measurement is. The problem with having more length than this is that fewer women are going to be able to take it all without experiencing discomfort. From everything I’ve learned here and elsewhere, 8” of exposed dick is already pushing it for many women! I don’t know about you, but I want to thrust all of my dick into a woman, not just a portion of it.
Even if you don’t want to add more girth, doing exercises like jelqing and light stretching is good for the health of your penis. It can also make your erections stronger. These exercises, along with clamping and pumping, can also make your flaccid size (both length and girth) bigger. So there is a lot that you can gain from PE, in addition to extra length.
By the way, welcome to the forum! :)