The point is "we" have no clue what our boats are at pressure wise. 3 psi is pretty good for "most" tube sets. You will get the proper tube pressures soon enough. Someone else must own a Caribe and have the manual/knowledge.
Case in point: Saturday I was bringing my tube pressure up for Sundays adventure. I inflated the keel pushing on it until it felt right, and banging on the tubes until they felt right. Then got out the pressure gauge, and checked the tube pressures. The keel was at 6psi
(Should be at 3.5 psi), and the tubes were at 2 psi (Should be at 3 psi). I can get the rear tubes very close by how the conical ends feel and do not fold over. The front tube is harder to determine. Especially on my SIB the pressure makes a big difference in how it rides, and more importantly, handles.