You've never seen one but I happen to have photo on hand:
All the tabs are welded and the whole thing is sheetmetal. I can see weld burn on the other side for all the fins inside the converter.
Welding the spacer will help. With spacer moving between the flexplate and converter, you got 2 shear planes. This create a bending moment on the bolt instead of pure shear.
Oh well what does a fucking engineer knows anyway.
BTW I'll rather the bolts break than the engine trying to twist the flexplate off the converter.