@defuser - appreciate your question is a few months old but maybe you or others are still struggling with setting your tyre pressures?
The issue can be that even though you know the hot pressure target i.e. the pressure you want to be running out on track, you can only set tyre pressures cold.
In your case it looks like you are also struggling with the real world problem of the sun warming up the tyres and thus changing the pressures over when you set them cold. Unfortunately this can cause confusion because your references are now all over the place - for example, if you have worked out a cold pressure to track delta for each tyre, and the tyres have been sat in the sun with a different temperature, will the delta be the same or less? If less by how much? Etc.
Tyre pressures are so fundamental to car balance and performance yet so many people basically guess them - even if it is an educated guess.
What would be better would be to have absolute certainty around setting your tyre pressures. So that you were in complete control. That you knew exactly how to achieve whatever tyre pressure you wanted at each wheel, when ever you were out on track.
One way to approach this is to use a scaling factor and then correct for ambient and track temp variations (rule of thumb being 0.1 psi / degree).
If you've not heard of the scaling factor method, then I've written it out in some detail on my blog (link below), but in effect you are using a ratio of hot to cold pressures, to then very accurately establish a method for precisely setting your cold pressures.
It is super simple once you start doing it but I don't hear of many people approaching things this way so thought I'd share.
Best of luck
https://www.yourdatadriven.com/how-t...ly-every-time/