I have a similar setup and started with 12" coilovers. When fitted, I either had too much lift, or not enough "stuff" to optimize useful articulation. I ended up swapping them for 10", but might go to 12" someday .
Your hoops look much stronger than others I've seen. I don't think you need to remove them to add plates at this point. The ones I've heard of breaking were 2-point connected with shitty welds. Yours are 4-point-connected, so if the welds are decent, You've got many other places more likely to fail under stress.
Nice job so far. It'll be great to see how it turns out....

EDIT:

I've had a chance to sleep on this (It's morning in the UK) and wanted to add. I definitely think that the frame mounting point should be kept an eye on for signs of fatigue. It would also be worthwhile to consider strenthening options that do not include grinding off your current welds. Good luck and keep us posted on your rig...