It doesn't really matter what the beam of the boat is. The width of the transom is more relevant: if it sticks out too far you can have problems. A Janbenbav can carry a much bigger tender than a Contessa for example.
Of course if you aren't stuck with a half-boat you have more scope. My 11 ft tender fits comfortably between the hulls
-------------------- One hull good, two hulls better.