[Iguana]

Guys, think about it like this, your tunica ultimately defines the size and shape of your penis. When the smooth muscle inflates with blood it eventually expands until the tunica restricts it (if your EQ is good.) The more the smooth muscle expands, the more rigid your erection.

If your BPFSL is much longer that your BPEL this means your tunica can stretch longer than your smooth muscle can effectively expand.
Else, they would be close in relation.

So, logically, if your tuncia is longer (indicated by BPFSL) then you would work your smooth muscle (i.e. jelq, clamp, etc.)
The inverse would also be true. If your BPEL is about the same as your BPFSL, the your smooth muscle is expanding the tunica to it's limit. You would then want to stretch out the tunica.

Think of a bicycle tire. The tunica being the tire and the smooth muscle being the tube. If your tire was much larger than your tube you wouldn't stretch the tire. It would just make the problem worse. If your tunica (BPFSL) is much longer then the smooth muscle needs work.