How do you make 'proof colours' more accurate?

Interesting question which I do not have the answer. However I wonder if it has anything to do with how the icc profile is created with regards to paper OBAs. I make my own profiles with the older i1 pro and iMatch software. Problem with iMatch is I have no control over the making of the icc profile after measurement. Also as far as I am aware I cannot compensate for OBAs. The newer i1Pro2 can and I have been pondering on whether its worth my while upgrading. The paper I use at the moment is Ilford Prestige Smooth Gloss and Pearl. I suspect these have OBAs in them. When I soft proof in photoshop I get the same effect as you. However once my eyes have got used to the soft proof the colours are very accurate.