Hi AVB,
I have fitted a 1/2" x 77.15" Kevlar belt (K-Force B195404062) that is meant to replace the 954-04062 belt that the MTD Rover Raider owners manual specifies.
But yes, it does look too loose. Maybe I should search around for a genuine MTD belt to try out and measure up.
You are right - the 14/38 stands for a 14HP Briggs & Stratton and a 38" deck.