I wear my dropleg on the drive (empty).
Case the pistol. I keep my mags loaded (don't see anything in the statute saying you cant do that) and then I stick the mag not in my dropleg next to my pistol in the case (keep in mind, the pistol itself can't be loaded).
When I get to my destination, open the trunk and the pistol case, throw the mag in, release the slide, and insert the pistol into the holster.
Hope this helps.
-Jason