I would think 250 feet (Hey, what kind of Canadian are you, using feet instead of meters?!) is plenty of scope. If someone drops on your anchor, tradition allows you to scuttle 'em without warning. If someone way out of range simply goes Donald Duck...same rule applies. Sink 'em, then discuss terms before recovering any survivors.
As we say when racing, if you're gonna hit it, sink it good. If you leave no survivors you waste no time with the protest committee.