Thats what made me wonder about that prototype roll bar I looked at....Red/white 001 - sure seems that the roll bar would be a match
You may have stumbled on to something with your prototype vert roll bar find and this article. Since I am always suspiciuos of coincidences, perhaps MKII 2X1 was initially intended to be MKII 001 and somewhere along the line that changed. (I'd venture a guess the first MKII customer order may have insisted on that 001 number, and thus the change to 2X1 was created.)
I wish we could get some insight from the founding members of these SAAC cars. I had hoped Paul "PxTx" was going to have some luck getting Chris DiMarzo to join in here or contact me regarding some of the unique items that we're coming across before to much time passes and more details are forgotten or lost.
It's slow but I'm making some progress toward the next registry update.