This study investigates how two core metrics rooted in Dependency Grammar, Minimal Dependency Distance (MDD) and projectivity, predict sentence acceptability in Russian and Serbo-Croatian. Using exhaustive word order permutations in controlled five-word sentences, we model how these metrics relate to acceptability judgments in two psycholinguistic experiments. While MDD has been widely studied as a processing constraint, projectivity violations have received less attention in acceptability modeling. We show that both significantly affect judgments, with projectivity playing a surprisingly strong role. In addition, Serbo-Croatian’s rigid clitic placement provides a natural test case for disentangling grammatical from processing constraints. Our findings offer a computationally precise, dependency-based model of acceptability that advances cognitively grounded language modeling for free word order languages.