It looks like you have been passing on some offers. Is it because of the future tank size or the bargaining? If your main worry is the size of their new tank and you don't care (that much) about the $$, let me know as these would go into a 4500 gal. But if you can wait longer, I would most certainly do that. Perhaps try posting on CL too for more local attention.
Transporting large pbass is risky. The longer the distance, the exponentially higher the risk. On multiple hour trips, the usual survival rate is around 50%. Speaking from personal experience and that of others. These tend to die for no apparent reason while others take a trip fine. Stress, lower oxygen, and pH shift have been suspected.