[A/S] Tire pressure, etc.

[hilty@xxxxxxxxxxxxx]

My '90 Excella 25' has Goodyear Marathons, but they are load range C. 
I would prefer to have Ds, but I was not willing to replace the three 
good tires to upgrade when one went bad a while back. My own common 
sense says it would not be good to mix different load range tires on 
the same vehicle. If I were going to do that I would at least match
by axle, but even that doesn't sound good. Is there any KNOWN rule 
about this? I only ask about this because many times common sense 
tells us different things than actual real world empirical data
proves out. 

On another note, does anyone depressurize your tires when your
trailer is stored and pressure up when preparing for a trip?

Thanks,
JOhn H.