Questions about custom exhaust mods

I will be making some more mods to my 420G exhaust, to hopefully correct some issues,
and would like some opinions from this list, and will also ask my exhaust specialist.

I previously fitted NOS downpipes, but I suspect they are from a 3.8 MKX, as they prevent me dropping the trans pan, unlike the originals, which were rusted.

These go to a small mixing muffler at the front, then large stainless mufflers, and SS straight pipes, which are minus the factory hot dog mufflers

Question 1)

The downpipes are going to be altered, including me welding bolt up flanges.

I am thinking to introduce the following SS flex pipe and clamps. This will enable me to end the pipes where I need to without bending, and take up flex/vibration from engine/body movement
(hopefully)…all comments and advice gratefully received

If this were mine, I would go with solid pipes and have someone make the bends for me. Never had much luck with the flex. It seems to burn up fairly quickly.
Phillip