Let's be honest, the weapons allowed on planes aren't enough. The only thing allowed by the rules are Vickers and bombs that do little to no damage to ships. ExplanationAlmost all mid-late WW2 planes had a 20mm cannon, some even had two, three or more. They are small, efficient and can carry a decent amount of ammo. They were very common in that time, very famous planes like the Spitfire, FW 190 (it had 4 along with 2 mgs) and the IL-2 had 20mms. Use in the server The 20mm cannon would deal a lot of damage to aircraft and airships and medium damage to ships (More than the Vickers but not a lot for balance issues). Here are my suggestions on ammo, price, firing rate, sounds, appearance and location to buy it. Price: 80 each (Limit of 2 cannons) Ammo: 120 bullets Firing rate: 400 RPM (They fired more bullets per minute in real life, its just for balance in-game) Sound: I don't know anything about sound design, but this could be a good sound to have. Appearance: I think the 20mm Hispano cannon MK5 would be good Location: I'm unsure about this one, you could buy it at entities or at the rig, if it was bought on the rig maybe it could have some AP and HE variants. Well this is mostly it, I just think that the Vickers aren't enough, please take in mind that I don't know anything about making addons in Gmod, just 3D Modeling.