Eamon, don't do this. A clamp on filter will cause problems in the rain, but more important is that the carb will fall off. The stock carb is connected on both sides by rubber manifolds. If you remove one , the other (from carb to engine) won't take the stress. It will rip. Then the carb falls off. While it is in the process of ripping the carb will flop around and vibrate. This causes the gas to foam. It won't flow properly and the engine won't run properly. You can fabricate a bracket to support the carb, but the stock carb is limited as to how much it will flow no matter how it is jetted. Get the Amal 30MM kit. It bolts on and flows better. It will eliminate all the problems you are going to cause for your self.
Eamon, we should try to get the Seattle Bullets together at one of the last old skool Seattle hangouts one of these days. Cheers, Jon