A500-42RH swap question

I built/modified my own stout lower crossmember and thought I could get a away with not creating the upper part of the crossmember.
After a few months of driving I had the car on my lift again and noticed the factory spotwelds were tearing loose from the floorboards.
I put welds along both sides of the crossmember and floorboards which stopped the process.
The (dynamic) weight of the heavier transmission puts a lot more force on the crossmember area.