Yes, we started using a cyberskin extension sleve but there were some problems with it. 1, it wasnt realy made for someone as small as me cause I couldnt get a tight fit inside & cause enough friction for it to not slip. 2, I always came inside it way before she was ready for me to & once you cum in one of those things it will slide all the way off & you will never get it back on a limp peter. So, yes I just use the standard Vac-U-Loc harness that was made with the intention of a lady wearing it but nobody told me that I couldnt wear it too.Yes, it seems to me that the hollow ones wouldn't really do much for the man as it wouldn't be providing much stimulation to him and that wouldn't be desired anyway, as what good would it be if he reached orgasm before the lady did? Then she would not only have a useless limp white dick, but perpetually hard black one that just rolled over and fell asleep!
I would think just using a standard strap-on system with different sizes and styles for the lady's pleasure would work more efficiently as it would focus on her pleasure alone.
Although, I do see a possibility for the hollow style to be used as a form of humiliation play for a cuckolding couple similar to the use of the type dildo that is strapped on as a mouth gag.
Try a website called extremerestraints.com. They have some that are extendes but are quite thick and dont slip off. My wife loves it. Good luck
There are 2 in particular that you have to slip your balls through a hole that can be a little uncomfortable but they are worth it. This is the one my wife loves http://www.extremerestraints.com/penis-extenders_189/xl-black-mamba-cock-sheath_5137.html.
