Re: swarm trap size
It is not really a matter of what size is "sufficient", in my opinion. Swarms move into boxes of all different sizes, including 5 frame nucs. Just take a look at one of the Ollie (odfrank) swarm trapping threads!
The 40 liter size often bandied about is approximately 10 gallons, and is approximately the volume of a 10 frame deep.
You can read Seeley's Swarm Trap study here:
I make my swarm traps out of equipment built for other purposes. Make it do double duty.
USDA Zone 7A Elevation 1400 ft