First let me say that your tyre stems (and your Motorhome) look great. That should make checking the tyre pressure a breeze.
Second I would like to apoligise for not answering your questions in a more timely fashion, but we were mourning the loss of our feline travelling companion Clancy who was killed by a hit and run driver on Wednesday.
As we live in an area where the nearest weight scale is about an hour and a half away, I needed an alternative method to determine the correct inflation pressure for my tyres. I used the chalk method; where you put a wide chalk line accross your tyre and then drive it forward about 100yards. Inspecting the chalk mark on the tyre will indicate whether you need to add or remove pressure. If the chalk is still on the outside edges of the tyre, but mostly gone from the middle then the tyre is overinflated, the opposite would indicate an underinflation situation. I adjusted pressures untill the chalk mark was worn the same accross the surface of the tyre. Because the motorhomes weight is not perfectly balanced, I found that the drivers side required about 8psi more then the passanger side. I inflated both tyres to the drivers side result plus another 5psi, I ended up with 67 psi in the fronts. I did the same for the rear duals, equalizing the pressure on all four tyres, ended up at 58psi.
I check the temperature at the outside areas and the middle of each tread. I am looking for equal temperatures +/- 5 degrees. The temperature of each tyre is allways a little different- weight distribution, road crown etc. but have with one exception been within my arbitrary limits. The only time it wasn't my temperature was much warmer on the outside tread area. Gauge checking the pressure showed 56psi. After pumping it back up to 70psi, I had it checked at a tyre shop--leaking valve core.Cheap and easy.
After having said all that, I am going to invest in a tyre pressure monitoring system, and the next time I take it by the govt weigh station I will get it weighed.