The previously reported MINLP formulation was modified in order to reduce the number of required binary variables. This is expected to advance the overall efficiency in solving the MINLP as less decision variables have to be determined in the global optimization. The main difference is that in the presented formulation the tree is always fully constructed for a given number of pre-defined tree layers NL. The predictor variables and constants can only be assigned to the lowest layer. The inclusion of an identity function allows to pass up the values without any change to a higher layer in the expression trees.