I decided to attach the sill portion with bolts drilling slightly oversized holes in the brace and then tapping the holes in the native rocker sill. I trimmed the edges to fit as perfectly as I could, filled underside contact areas w/panel bonding epoxy (E6000), then put the bolts in. I welded the shafts of the bolts and cut them flush with the brace before completing the welds around the bolts, edges at the fore/aft frame bars, and along the floor pan portion.
With the roof seams welded and braced, and the inner rocker panels strengthened, this should significantly reduce the torsional weakness inherent in this design w/o having to spend $1200+ on an aftermarket kit …at least that’s the hope/plan.
I forgot to mention, the rocker braces were made out of 3/16 steel. Adds a bit of weight to the car, but still far less than one of the stiffening kits.
Cool idea. I would like to do something like that too.
what size metal?
Lots of pics of the install please
Looks great! Keep us posted. Def like the rocker stiffening idea
It’s been almost a year since I posted any updates. I’ve reached my limit of abilities with the last stiffening/panel issues I posted above. I found a local guy who’s very talented, though minimally motivated at times, to tackle the last/finer issues. He has repaired all the panel gaps, reworked the gas filler neck to open out the side of the driver-side fins, and installed a new air-ride system (w/my existing suspension upgrades). We’re nearly to paint, hopefully in the next week or two …weather permitting here in N.Florida. 
...Here's the 'Hard Truth' as I see it. Your welds are Lousy!! Your tack welds are 'OK'. But, the welding you have done under the chassis, are Not welds!! There is No 'Weld Prep' and there is No 'Penetration' into the Base Metal, which is what welding is all about.
I suggest you STOP welding Unprepped Steel, and take a Welding Course at your local J.C. Learn how to weld prep and How to use a welder Correctly. 'Flux-Core' is Very difficult to work with. Those who recommended welding under a Gas 'Shield' are Correct! I prefer Mig as One Hand is FREE, and TIG takes Both hands to perform. You won't pass the 'Fundamentals' Welding course, until you can demonstrate All Arc welding up to 'Vertical' beads, and Especially Oxy-Accetelene Welding. 'Over-Head' welding, among many other procedures, is demonstrated before becoming a Certified Weldor. It All starts with the 'Weld-Prep'.
Welds done badly are NOT welds...they will Break the moment they are Stressed.
And if you go to sell the car, the prospected customer will see welding, often described as "a Bunch of Grapes". For now your just wasting your time!!
No amount of Practice is going to make up for the lack of Training to Know What You are doing and how to Weld Correctly. And you're suppose to practice on Scrap and Not on the car itself. Did I say this was a Hard Truth?!
MJ
P.S. Are You aware that ARC* Welding on any Car, before, First Disconnecting the Battery AND the Alternator...Stands the Risk of Knocking-Out One Or More Diodes in the Alternator, and Possibly Burn-Out the Voltage Regulator??
* ARC as in any 'Electric'...Rod/Electrode (Lincoln style), MIG or TIG, and Plasma Cutter.
