Well, it looks like most of the above so called tyre experts above need to take Tyres 101 again.
The tyre manufacturer marks the sidewall with the absolute maximum tyre pressure you should use, and the maximum load you should use.
If you are not running that maximum load (and our VXs don't) then you don't use the maximum pressure.
That is where the vehicle manufacturers recommendation come into play. If you use the "standard" tyre size nominated by Isuzu, you would run at the Isuzu nominated pressures. That is your starting point.
Then, if you are running a wider, or narrower tyre, you adjust that pressure (Higher for a narrow tyre, lower for a wider tyre).
There is then more room for adjustment for the loads you might carry on a regular basis, or for personal taste.
Then the final check is the chalk line across the thread width, and see if it wears off evenly. That will give you maximum tyre life.

Of course you can always deflate a bit for softer ride, and pay more for gas and tyres.
Or over inflate for a harsher ride, and pay less for gas but more for tyres.
Your choice.

But to automatically inflate to the tyre manufacturers maximum with our little VXs, is total BS.

PK