Gotta disagree here... it's not the thickness of the wall of the chassis that's doing the supporting (the "few millimeters" you referred to)... rather, it's the length and width of the wall of the chassis that's doing the supporting... it would take a huge amount of forced for the pin to tear through the wall.

It's going to add a ton of strength to the assembly, and remove a lot of stress from the sides of the differential cases.

As I said before, the stock forks do very little to support the hingepin mounts since they're unsupported at their open ends... and if you look at how the chassis's broke, that's exactly what happened... the hingpin mounts tore out towards the open ends of the forks.

I considered filling the plastic supports with epoxy, as you suggested, or even adding additional ribs, but decided that this would do very little compared to what this mod was already doing... for the hingeipin mounts to tear out now, first the pins have to tear through the walls of the chassis.

And yes, I agree that this mod may cause breaks to happen elsewhere, but I'd rather have something else break rather than the chassis.