Wearing several items on one slot,especially rings

[carn]

"Of course, a character may carry or possess as many items of the same type as he wishes. However, additional items beyond those in the slots listed above have no effect."

The rules seem to imply that a PCcan wear more than two rings on his hands (not unrealistic), but magical rings beyond 2 have no effect.

So a PC dons a ring of protection, a minor ring of spell storing and then attempts to slip a ring of invisibility over one of the free fingers. What happens? Game effects?

Assuming the result is something like "2 rings active, 3rd and last doned ring non active" could the wearer spend a move action to dislodge 2nd ring, make use of 3rd ring, then spend a move action to don 2nd ring again (meaning no 1st and 3rd occupying slots, with 2nd dormant) and at later time swap rings again with 2 move actions?
Or would it be another kind of action?

What happens if one ring has spell effect with a defined duration (as i assume invis ring has)? Is the spell ended by putting another ring in the slot?

[LazarX]

The specifics are a DM's call. My rule is simple. The first two rings work, none others put on will function until one of the earlier two is removed. If you put multiple rings on at a time, none of them work.

[Umbranus]

I think swapping rings in that way should work.
But you should ask your gm is the first ring or the last ring per hand works. And swapping rings can disrupt ongoing effects that only apply after wearing them for a day or longer (like ring of sustenance).