We recently took in a cat (backstory here: Can I guess on information requested by pet insurance forms?). He's been fighting with other toms in the area; sometimes in defense, though also as the aggressor. He stays in at night, but gets agitated if kept in during the day, even when stimulated, spending a maximum of 30 minutes inside before he wants to go out again.
With humans he's perfectly behaved, having befriended most neighbours and visitors, and even allowing us to put him in his carrier without too much of a struggle and with no clawing despite disliking it as much as any other cat.
I've seen lots of advice on getting two cats to live together as housemates, but can't find much on neighbouring cats belonging to different owners. Are there ways to reduce his aggression short of keeping him inside or moving house?