As software systems have grown large and complex in the last few years, the problems with which Model-Driven Development has to cope have increased at the same pace. In particular, the need to improve the performance and scalability of model transformations has become a critical issue. In previous work we introduced LinTra, a model transformation platform for the parallel execution of out-place model transformations. Nevertheless, in-place model transformations are required in several contexts and domains as well. In this paper we discuss the fundamentals of in-place model transformations in the light of their parallel execution and provide LinTra with an in-place execution mode.