When I have used specular for this in the used as a spot the position of the highlight in the eyes is dependant on just where that spot is placed.  I normally point the spot at the models head and then move the light directly in front of the model adjusting the height of the light to lift the highlight to the upper eye.  I then tend to move the light left or right to move he highlight off centre.

 

 

I use Poser 13 on Windows 11 - For Scene set up I use a Geekcom A5 -  Ryzen 9 5900HX, with 64 gig ram and 3 TB  storage, mini PC with final rendering done on normal sized desktop using an AMD Ryzen Threadipper 1950X CPU, Corsair Hydro H100i CPU cooler, 3XS EVGA GTX 1080i SC with 11g Ram, 4 X 16gig Corsair DDR4 Ram and a Corsair RM 100 PSU .   The desktop is in a remote location with rendering done via Queue Manager which gives me a clearer desktop and quieter computer room.