Set the degree of each jet variable to match its order, as in Proposition 6.6 (c) of P. Vojta, Jets via Hasse-Schmidt Derivations. This guarantees that the output of jets is homogeneous.
With Projective=>true the jet variables of order zero have degree 0, therefore no heft vector exist for the ambient ring of the jets. As a result, certain computations will not be supported, and others may run more slowly. See heft vectors for more information.