The symplectic group $\mathrm{Sp}_n(q)$ acts on $\mathrm{GL}_{2n}(q)$ by conjugation. All the literature I have found concerning the orbits of action of this kind is "Unipotent conjugacy classes in general linear groups" by Alperin, which is not really about what I am looking for.
Is there any work referring to this action and its orbits?