Fly as a capital ship

There is a trick that FREDders can do while FREDding a missiion that can allow them to pilot ships that they normally can't. This includes freighters, cruisers, capital ships, and even the Colossus.

For starters, suppose that you have 2 ships in a mission. Alpha 1 is in a Loki, while Beta 1 happens to be an Orion. Save the game, start FreeSpace 2, go to the mission simulator, and select the mission. When you're there, go to ship selection and there will be 2 icons, Alpha 1 (you) is a Loki, and Beta 1 is an Orion. Switch those 2 ships and start the mission. Congratulations, you're flying an Orion now.

Beam cannons won't fire

If your using FSO and sent Beam cannons unlocked by default in the Mission SPEC, all beam cannons will fire normally, except for yours. To make your beam cannons fire normally, you have to set a Beam-free-all SEXP on yourself.