Hi there,
Does he seem like he's getting enough sleep overall ie does he seem tired or well rested when he gets up and what's his mood like?
At this age it's not uncommon for LO's nights to shorten a bit until they drop the nap, so you might not be able to get a later WU just with Gro clock alone.
I think at this stage you could either just stick with 10.5hr nights and 1.5 hr nap (if he is happy with it, why change?) but poss move BT later by say 15 mins to move WU later (but you have to decide what you prefer, earlier BT or later WU), or you could try capping nap a bit more to see if that will lengthen his night for you. Does he mind if you wake him from naps? (Some LOs hate it).
For us, we preferred to cap L's nap (until she dropped it) to keep nights as long as poss (she also got more total overall sleep like that).
What do you think?
Other option like hena said is to move Gro clock later and treat it as 'up' time not wake time , so you get more time in bed. But if he wakes you once he's awake anyway, even if he stays in his room, then maybe that's not your preferred solution?