Here my experience of the skywagon
Sea Level, standard day nil wind.
220 meters is good for takeoff with 4 onboard plus gear on a 300 HP C185 in a pair of good hands, add another 30 for fudge factor or not being current. So if you can bank on 300 to 400 meters in the same conditions as a good workable airstrip for both the C180 and C185. (they take off and land in similar distance but the C185 will climb out better, with a larger load)
Landing is where the skill level really meets the road, and is very dependent on braking effect (or hill slope as in PNG and NZ).