Any time that you have any Z or S bend like the one I am showing here on a DSE sub.. you will have flex.. I know this cause I have my car on the jig.. & can lift it & it will flex.. Down bars help allot in my opinion.. I have been doing testing & analyzing flex point on chassis's lately.. I have figured how I am going to stiffen it up in this area.. 2nd gens are allot stiffer when it comes to chassis & body configuration.. weak link on first gens are floor designs..
Hotckis down bars work.. or any other one's out in the market help.. If I set up down bars.. I set them with engine load on the front wheels.. welding is allot stronger than bolt on.. IMO..
Here is another pic of the way it was done in Trans AM racing.. 68 Penske/Donahue engine bay.. look @ the way the bars come in @ a angle to the bend on the chassis that tie into the cage..