The Transformation-Interaction-Rational is a representation for symbolic regression that limits the search space of function forms to well structured functions enabling the use of efficient numerical coefficient determination. The performance of using Genetic Programming with this representation was substantially better than with its predecessor (Interaction-Transformation) while ranking close to the state-of-the-art on a contemporary Symbolic Regression benchmark. In this same benchmark, we observed that the performance could be further improved with an additional selective pressure on smaller datasets for the expression size, thus creating smaller expressions and generalizing better. This was verified with a penalization term applied to the fitness measure together with heuristic rules to determine what is a small dataset. Possibly a better strategy is to adopt a multi-objective search to find a set of non-dominated solutions taking accuracy and model size in consideration. This will automatically stimulate the preference for simpler models whenever two equally accurate model exists, possibly the need for heuristic rules and penalty functions. In this paper, we extend the evolution library used by TIR to support multi-objective optimization, specifically the NSGA-II algorithm, and apply that to the same benchmark. The results show that the use of multi-objective optimization improves the results on a selection of the benchmarks increasing the overall rank of the algorithm to a second place in the benchmark. However, this strategy is still sensitive to overfitting on small data sets.