Narrowing a 8 3/4 diff.

Each side of the joint should have been ground to a 45 degree to about half of it's thickness, creating a nice "V" for your initial weld. Trying to burn a heavy enough weld to penetrate your overall thickness is not good technique, and is why you have voids in your welds that shown in the X-ray. You're not wrong, there are just better practices to follow.