IIRC, lowering pressures on the 19.5 tires is not a good thing like on the 16" equals I've had. As I recall, the rim to tire locking mechanism is not as strong from a lower psi standpoint. So running 50-70 lbs in the 285-19.5 that one would want with a pickup, might damage them sooner than later.
I would agree with Brian too, on the Double coins are not as good per say as the M or T branded tires. BUT< if one drives 10K a year, vs 20-30K miles.....as I am in my navistar currently......I'l year wear out the tires way before I will the tread part. So going cheap as I did for the fronts last time around is working out well!
Marty