I have a PA piercing myself but I wouldn't really recommend this for chasity. The forskin & PA piercing are both too shallow to hold the pressure an erection can generate. (although, this varies per person. if you have a very weak erection you may be alright.)
I'd say the forskin is out for sure. The average tissue there is just too thin & the tension will force the hole to either stretch or migrate. A PA may work for the reasons above, but having mine I don't recommend it as much. (it is great for play sessions & minor pulling on it is very enjoyable.)
What I do recommend though, is an Apadravyas. <a href="cgi.bmezine.com/cgi-bin/glossary.exe?sea...a&full=yes"
This goes through the glans itself, which is a lot thicker & more resilient to pressure. It would only take a little creativity to modify jewelry & locks or something to make this into a chasity piercing. Im thinking of upgrading my PA to an AP & maybe getting a Guiche to lock it to (<a href="cgi.bmezine.com/cgi-bin/glossary.exe?sea...e&full=yes"
Plus, the healing time required for these makes for an enjoyable chaste session by itself. My PA was mostly healed in 4-5 weeks, but we waited a full 6 before doing anything with it. I'm told an AP takes longer though.
PS. just reread your post - not sure how well this would work for an un-cut shaft. anyone have experience with that aspect?