Custom projection matrices make shadows impossible

Hi all,

I am experimenting with custom projection matrices for a current project. However, it seems that neither realtime directional shadows nor deferred lighting are available (shadows disappear/seem to be offset). I think the problem relates to some other questions (all with zero answers) regarding the impossibility to use render textures with custom projections.

Could someone confirm that it is not possible, to be sure? Or (which would be better :D) is there a workaround, maybe by overwriting the standard render pipeline? I understand that this isn't a feature used by many people, but in some cases those custom projections are quite useful.

Felix