Nobody here in over a decade can clearly delineate what forces the SFC's are exactly resisting, so the thinking "it can't hurt" likely applies.
RE the snipped out section above, I thought at one point over all these years we had talked about how Mopar's Hustle Parts engineers had developed the sub-frame connectors to resist the beaming motion of drag launches way back in the early 70s.
Did you read the BBD Tech Pages article I linked in my first post?
The rear frame rails are a near perfect fit for the ID of a 2x3" 1/8-wall box tube when it's oriented that way. Which is also readily available at both steel places in my area... don't think they had anything but 1/16 and 1/8 anyway.
Although the connector would be stronger in flexion if oriented vertically, much longer floor cuts/welding would be required also.
Anyway I originally just asked whether to flatten the curved protrusion on the left T-bar crossmember or to notch the plate/connector
But this is one of the topics (like 8-3/4 vs. Dana) which is guaranteed to start a lively discussion
IMO, unless rules require it or you are pursing a more full frame approach, there really isn't the need for .125 wall structural reinforcements pieces in a uni-body construction. However, it is a common approach taken by many that if large is good, bigger is even better. If one is willing to add weight for structural improvements, much greater gains can be made with stitch welding factory structure over adding a bunch of eight inch wall structural components. Since your car is complete, proceed with the thick wall connectors and enjoy the increase in rigidity they will provide.
