Hmmm, I know their coats get dry, but I don't know about hairloss. Have you seen him overgrooming or anything? I suppose the drier coat might be itchier?
It may be that he needs 1.75u. Do you have any mid-cycle spot checks on this dose to see what the low of the cycle might be? That 2u seemed too strong, but sometimes only a minor adjustment is needed. Could be the 1.5 is too little. Hard to be sure though until you have some more data - some cats get a good nadir and just tend to have higher PSs, while some have longer duration and seem to get lower PSs.