It might not be relevant, but in the Rules As Written, a 26 roll for potential results in a 39 as the potential stat (Character Law and Campaign Law, red band edition of 1989, table 15.1.1 'Stat Potential Table', p. 38).
You could have a 26/26 if you rolled a 26 for temporary and then 20 or less for potential, though, which is the case here I believe? In that case, yes, Peter is right, there is no way to raise that.