I'm sure your right, I'll probably put in the penetrations just to be on the safe side. I suppose what I was wondering is if the gantry sides were deflecting while the side/torsion box joints remained rigid (in which case my sides should resist this more). Or of the whole gantry frame was moving like a paralellogram, ie: the joints were moving as well as the sides deflecting (in which case my mod won't do any good). In either case I'm still not seeing how adding more horizontals will help. Wouldn't they have to be braced at an angle to prevent flex?