From the looks of this fish, the maternal species is lima shovelnose, as hybrids inherit more of the maternal features than paternal features, including size. So I'd guess it would not exceed 2' or not by much.
I'd also mention that this hybrid has been known for a long time, a decade or longer and the fact that it has never taken off in the fashion of TSNxRTC and TSNxLeiarius to me says that they are not viable, which in turn means that they stand a zero to little chance to reach adulthood or live a long enough life.
Which serves its producers, sellers and buyers right, in my humble opinion.