once you go thought agate made by the 'stargate' plugin, if you try to go back it bounces you off saying
"this portal goes nowhere"

So, I just added an option "bounceback" to the config that you can set to false which should solve this issue. Yes, there will still probably be a message saying this portal goes nowhere but that's just how it's gonna be until a better fix can be had. http://ci.onarandombox.com/job/Multiverse-NetherPortals/629/

You have probably figured it out by now, but I have found a (hopefully) temporary workaround. create a new world, and make it hidden. Then, use /mvnp link nether [World] [Hidden_World]. Unless someone on the server will create a standard portal, the hidden one will never be used, and you can access your portal made by Stargate.