I seem to remember some double-lugs that have a cylinder base, to fit into a standard lug, thus allowing you to terminate 2 wires.
What about adding a non-thermal breaker to feed the TVSS. Most TVSS manufacturers have some fusing installed, and allow this type of connection.
As a last resort, what about installing a compression type of splice onto the existing wire, kind of like the type some utilities use to connect service conductors. Of course, these will need to have either a cover installed, or may need to be taped up.
Installing 2 wires in a lug rated for only 1 is a code violtation, and should not be done.
Rick Miell