Yeah, thats about right with cranes platinotype. !.3, 1.4 is about the highest D max I have ever been able to get. But his should not bother you, I have not seen What Clay put in the portfolio, but if you look at my print, you see there is what Arentz calls "convincing" blacks.
Dont worry about getting very, very black tones, just that they "look" black. This is one of the most difficult parts about pt printing.