Change the selling price so that with Texas's current drop rates it equals out to about the same credit/time ratio as the other routes. Remember that the radiation in the *negra fields take a big bite out of ships. Anything durable enough to collect a full hold will come back with a few hundred k's worth of damage.
Culebra and Viqeues form a big part of my roleplay as a career Junker. I can assure you my status, as a result of these changes to scrap metal collection, is set to STOKED.:)