End ChangeGroup.
Section Morphpre.
Variables (aT rT : finGroupType) (D : {group aT}) (f : {morphism D >-> rT}).
Variables (G : {group rT}) (n : nat) (rG : mx_representation F G n).
Local Notation rGf := (morphpre_repr f rG).
Section Stabilisers.
Variables (m : nat) (U : 'M[F]_(m, n)).

Lemma morphpre_mx_irr :
G \subset f @* D -> (mx_irreducible rGf <-> mx_irreducible rG).