I do a heavily modified version of Del's route, which only passes through sigma 13 once.
Im gonna go ahead and put it here, otherwise i'll forget it myself soon.
Starting from planet Cambridge.
Planet Cambridge to Planet Baden Baden with Prisoners
Planet Baden Baden to Planet Stuttgart with... something that makes profit (dont run empty)
Planet Stuttgart to Luxury Liner Hawaii with Luxury Food
Luxury Liner Hawaii to Beaumont base with Artifacts
Beaumont base to Casablanca base with Slaves
Casablanca base to Gran Canaria with Diamonds
Gran Canaria to Planet Honshu with Deuterium (note, I dont go through Bretonia)
Planet Honshu to Mull base with Plutonium
Mull base to Planet California with Gold (I think...)
Planet California to LD-14 with Boron
LD-14 to Planet Malta with MOX
Planet Malta to Planet Nuremburg with Cardimine
Planet Nuremburg to Freeport 9 with Engine components
Freeport 9 to Planet Cambridge with Alien Organisms
Its a great run, and while you can run into hiccups with the local law enforcement (Bretonia in particular, since the Liberty types stick to New York), it keeps me much more interested in trading than your regular 2 to 4 stop run. A good share of... contraband in there too, to liven your day. Going through Sigma 13 once can't be helped, but at least its not with Diamonds eh? I'll leave you to find the safest/fastest routes out there.
