I haven't done patches for long, but noticed three things:
-- When placed on my butt, I bent over to stretch out the skin, attached the patch, and when I stood up, the patch sort of wrinkled as my skin in-stretched. It made me think the patch to skin contact might be less. This made me move the location to the front, just below panty line
-- I too found a little dark line around the outside after I removed the patch. I presumed it was lint/dust from panties going up/down.
-- They have stayed attached like I was born with them. After I had a bit of trouble with the first one (Operator error), the rest have stayed on so well they were tough to get off even. And that includes soaking them in a Jacuzzi spa a few times (without clothing to hold them close...). Someone mentioned different manufacturers. Mine are from Sandoz. I am pretty sure they use Gorilla glue on them... :-)
So, where do y'all place your patch(es), and how does it work out for you? Since you have to rotate locations, what places to you cycle through? RobinTx suggested putting them where fat is. That does give a lot of options for me... Is further up the torso OK?