I've made a couple for my BN6, though they're both currently in the attic of my shop bldg. The first one (circa 1987) reaches 4" above my helmeted head, and the top could *almost* be stretched over it__A small
gusset of top material at the B-pillar would've reached the turn-fastener.
The cross-bar/diagonal was modified from this original configuration, but this shows the extensiveness of the structure; IIRC, there were fifteen (15) bolt-in mounting points (the number of actual 1/2 L9 fasteners was roughly 4X that).
Several years later, show in the car:
Some more pictures from that day here:
https://spcarsplus.com/gallery3/index.php/Healey/1st_time_in_public
A couple years later, I reverted to just a single rear hoop; fits completely under an unmodified soft top (no idea about fitting under a hdtp). I figured if I ever did "real" (Dougie-style) track events, I'd have to do more bracing at the bends, but
the foundation does conform to current SCCA GCR specs fo diameter and wall thickness for the weight of the car:
More pics of this 2nd iteration, during fabrication:
https://spcarsplus.com/gallery3/index.php/tube_works
I'm sure (I KNOW) I have more pics, but in a hurry to get out the door and go to lunch...