The bottom picture of post 119 is of my car. The fab guy that did that has told me that he has done a few cars with the t-bar triangulated back into the sub-frame connectors with no troubles yet. In my case one way or the other, either with Dillinger parts or a HemiDeny k-frame I will be losing the t-bars. As to the amount of power you lose, from what little I know, that is very variable. The 4l80 is is a bit of a pig...using factory stuff. Largely because the oem t/c weighs as much as a boat anchor. But at the same time with the right parts it can easily with stand 1500 hp. I think that you just have to pick your poison. None of the od transmissions are perfect. Take a GV unit behind any dinosaur 3 speed. If you have a loose convertor you may end up running around with the convertor slipping. Maybe not the case with a low powered dd but very possible with a high powered street car, spoke with Lenny at Ultimate Convertor a while back and he was fighting that very problem with a customer and his HEMI Dart. When the convertor was loose enough to perform at the strip it would slip on the street while the od was engaged. When it was tight enough to not slip on the street it was to tight to allow the car to launch well at the strip. Solution, a lock up convertor. Which opens up the need to do some cutting on the car. Just like most things in life, there is no one "right" answer. No matter which way you go you will always run into the nay sayers. Such is life.
