I recently had a short discussion with a fabricator I chose to use for the first time, always a chance for an education. I mentioned that during modeling I would model to the outside dimensions even though they then use inside dimensions plus their allowance. When they mentioned inside I immediately thought that they meant the tangent point as that is where an allowance would start and be calculated from.
That was not the case and what a surprise! That was also without respect to the actual delivered material thickness. This made me think of the one time I received a model that was done to the tangent points. What HELL that was remodeling that one to outsides as all of our bend radii were different! We did use the exported flat to send to CAM and those would have never worked.