Possible to limit a link type so only one (or two) specific work item types can be chosen?

I would like to link a custom work item "system" with a custom work item "systemversion". Since I wanted those links for the users to be able to move back and forth between the items, I created a new link type.
But I can't seem to be able to limit the type that can be selected to "systemversion" so no one could add a defect or anything else.

I also have another scenario where two different work item types would be allowed.