It is a common misconception that the max psi values provided by the mfr will apply to all travel settings. Even if you phone the customer support line, you'll likely get someone simply referring to the published max psi specifications which really only apply to the fork's longest travel setting, and you can't get them to discuss otherwise because they have legal issues they need to avoid and the guy on the phone doesn't have the authority to say otherwise. The single thing the mfr is telling you, is not to exceed the maximum peak (fully compressed) air rating for the fork achieved when the fork is set to its maximum travel length.

Explanation:

When a fork is set up with less travel the air camber is typically reduced, and so when fully compressed the maximum psi it can achieve is also reduced. For example, if you take a fork with a maximum travel length of 160mm and reduce it to 120mm, in most forks you are taking away 40mm of air camber. That is 40mm less air you have available to compress, thus the fully compressed peak psi value will be much lower than with the 160mm travel setup.

As a simple example, think of a floor pump for your tires. If you block the tire valve so no air will exit the hose (ie: attach to a tire but with the tire valve closed), when you use the full pump stroke and record the maximum air pressure you generated, you will see this is much higher than when you reduce the pump stroke to something less (ie: try 75%). Although you may now think there is some 25% more headroom (extra air) you can add to the base/starting pressure, that is not entirely accurate because air springs/shocks are not linear. However, the important point is... yes, there will be spare psi headroom available when you reduce the stroke from the longest length the mfr used to specify the max psi allowed.

Unfortunately manufacturers do not post max psi values for each travel length, nor do they post max psi values for when volume reducers / tokens are added. For this last point, here is a good webpage describing the effect... https://bikeco.com/volume-spacing-ca...r-explanation/ . I have not located a similar page describing the fork travel setting effect.

Bottom line, when your fork travel is set to less than the maximum travel, in most cases* the published maximum psi (calculated @ max travel length) can be exceeded without problem for shorter lengths.

* Forks where this may not apply are those which use fixed length separate inner air chambers instead of the fork stanchions (lowers). For example the new Fox 38 model. However, the vast majority of forks utilize the stanchions as their air chambers and so will be effected by various travel length setups.

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Caveat/CYA Statement: The above opinion is purely logical deduction and personal experience. Assess your needs and equipment accordingly.

FWIW: This is the sort of mtb tandem riding we do (onboard cams never show trail steepness). Many addnl videos posted as well...