They look great, really nice welding.
But looking at the last picture I think the the bushings took all the strength out of the mount.
If the roll bar is applying pressure to the floor pushing down the bushing will allow the arm to just swing down on the bolt a pivot point just like the lower control arm in the same picture. JMHO
Now if it were reversed with the bushing mounted the plate on the bottom of the tub and hard welded to the frame it would be trying to shear the bolt under pressure instead of pivoting the arm down. and would have added the extra strength you were looking for.