Series 3 Series III 88" Rear Tub and Defender 90 Tub sizes

I'm hoping to fit roll bar behind the front seats. It has to fit under my soft-top and replace the rickety canvas frame. I've seen a lot of nice (but flimsy looking) tub edge mounted ones but which are often for defenders. Are the tub sizes the same?

My military series 3 doesn't seem to have many options unless the tub widths are the same.

Can I add, I realise these edge mounted systems are not the best design for roll over protection.

This is the kind of thing i'm looking at - https://www.gumtree.com/p/car-replacement-parts/land-rover-defender-military-roll-bar/1265910646

Across the tub is the same. While not of the same level of strength as a full roll over hoop with a diagonal bar the military one does increase protection.
In early days of trialing we were allowed to enter if we had the screen up and canvas hoops on.
Saw one or two go over on to their sides and it was enough to prevent them going any further protecting the crew and saving any further damage.