It appears that the uploader does not automatically scale the collider shape to the same extents as the main model. This means that you have to create separate collider shapes for each object, which gets tedious in a large build that includes many simple and physically similar objects, such as a house.
I would like to be able to have an option to perform this scaling automatically. It should also center the collider on the main model's bounding box. This way, I could simply create and specify a simple cube for all walls, floors, ceilings, etc. that only need a simple box shaped colliders.
Even better: Offer an additional option that automatically generates the simple cube shape and scales and centers it on the model. Note that these are two distinct cases, and if I have to pick one, I'd take the first (i.e. you have to specify the collider shape, but the scaling and centering is automagic.)
Obviously, this affects not just the physics of the build but also the acoustics, so its benefits are twofold. Did I mention that it'd be a huge time saver? ;)