  In light-front dynamics, form factors are traditionally computed with the
"good current" $J^+$ within the Drell-Yan frame $q^+=0$. Due to truncations
imposed in practical calculations, the from factor may acquire frame
dependence, which is often neglected. In this work, we explore the form factors
in more general frames, preserving the boost covariance. We find the frame
dependence of the elastic form factors for mesons is small in basis light-front
holography and related models with two-body Fock space truncation. We suggest
to use the difference between form factor results from Drell-Yan frame and the
"longitudinal frame" as a metric for the violation of the Lorentz symmetry due
to Fock space truncation.
