I have a Mk1 / Eunos and have just purchased a substantial chrome hoop roll over bar (the decorative type not the race track type). Only thing is I had to remove the cabin brace bar to fit it.
Does anybody know the degree to which this detracts fom the stiffness (right word ?) of the body shell/tub.
I don’t think the earlier models had that brace bar, could be mistaken on that.
I had style hoops fitted to my Mk1 (UK 96 model ) it also had the standard cabin brace fitted across, they bolted to each side on the seat belt towers. To have both fitted I removed the cabin brace and turned it around, it left room to fit the style bars. Couldn’t get the plastic trim caps back on though to cover the bolts, no big deal though.
Its a brace bar, not a stiffening bar. No one has measured it to determine additional stiffness. Mazda might have the numbers, because it was supposed to achieve side impact standard for the US.
Those one piece hoops are like a giant spring. they do nothing. You can get hoops (Racing Beat etc) that incorporate a cross bar.
Note fitting the 1.8 brace to a 1.6 model requires hacking the seatbelt trim, usually not very neatly.