HED seems to be equivocal on this matter. The 90 psi limit is documented, but elsewhere they say that higher pressure won’t damage the rim, but will add no benefit. Likely you are correct t that I picked the wrong rims (or more precisely a strain Colorado based house recommended the wrong rims) so HED guidance does not consider my case. Alas 28c tires will not fit my frame.

Thanks,

Michael