90 Soft Top - Roll Bar

Hi all - Ive got a wrag top on my old 90 and have just picked up a second hand safety devices roll hoop - the type that fits on top of the rear tub. My question is where does it fit? - does it go somewhere behind the first hoop or can it be modified to actually replace this hoop?
thanks steve

The ones i have seen completely replace the hoop, but usually some foam that fits around the pipe is helpful to keep it nice and tight. They usually use that foam insulation, the same as used in house boiler pipes.