Will this work or stress the body too much?

[MCMLXIX]

I have a 67 Chevelle that the frame has been boxed and braced. While this makes it much more rigid then stock, it’s still only one dimensional. I do not want a cage, so please don’t tell me to go that route… The car will never see the drag strip. It may see the occasional autoX but that’s it. It will be a daily driver that will need unobstructed access to the rear seats….



Ok… now for my idea.
Most of the weight is where the engine and transmission are located and the frame kicks up and out. What if I was to have some front down tubes made to connect the front of the frame at the core support up the firewall where the fenders meet it. Now I already plan to have the firewall smoothed. I would have some heavier plate welded under the dash to support the mounting point. The bar would have another plate and sandwich the firewall and bolt together. I found these nice connectors for the front…. See the pics below.





The general idea….





Now I will be using poly body mounts to further reduce body flex but this would be a 100% rigid mount.
Will this cause too much stress and cause the body to crack or tear at the firewall?