Our box bike frame and has 50mm of trail to give the best handling under all conditions.
However 50mm trail can be achieved in a number of ways.
The sketches below show various front end geometries. They all have 50mm of trail but all look very different and would handle very differently.
The parameter that makes these forks handle differently is "wheel flop".
Mathematically Wheel flop = Trail x Sine Headstock angle x Cosine headstock angle
Practically what this means is that as the steering on a bike is moved left and right the front end of the bike will rise and fall slightly. This is true for any bike that has some trail. This change is height gets more exaggerated for shallower head stock angles. So a bike with 50mm of trail but a 60° headstock angle will still have large amounts of wheel flop.
With our cargo bikes, wheel flop is more noticeable with the bike loaded. Extra weight on the front wheel makes it more difficult to "lift" the steering to find the straight ahead position. This makes the steering feel heavy and causes the bike to "fall in" on corners.
For this reason our box bikes have a steep head tube angle and low trail to strike the best compromise between loaded and unloaded handling.