"Only some wormholes are static: others wander. There's a mapping effort in progress, but I don't know which kind the one I came through was. As for the mass limit, give me a second... Low end of about 20 gigagrams per jump, high end of 1,800 gigagrams per jump: but if you do multiple jumps across the same wormhole, they compound. The highest recorded amount of mass a wormhole's been able to transmit before collapsing is in the vicinity of 5,000 gigagrams, but the low end is a tenth of that."