As I make progress on my Valkyrie, amazingly I make progress on my Vendetta as well. :) To make my Valkyrie duel purpose I attached some rare earth magnets on the underside of the wings. I also epoxied some rare earth magnets to my weapon systems. I've included a picture of how I did this on a spare twin-linked lascannon from a Land Raider kit.
The lascannon is put together as normal for a Land Raider. After the glue is dry I just trim off the parts on both sides that attaches them to the side sponson. I also cut into the hydraulic to make room for the magnet. The magnet has to be recessed into the weapon system or they look like the hang down too low on the wings.