When I purchased the car it came with an SBFS half-hood, but I was never very happy with the fit of the rear straps. The roll bar is an original 'low' one - the distance between the edge of the roof and the boot cover isn't that great and the wider 'V' shaped parts of the straps didn't clear the boot cover. (Whether this is by design or because the straps are the wrong type I couldn't say.) The bottom loop of the strap was fitted with a press stud and anchored by passing the loop through the roll bar bracket and clipping a cross piece into it.
It seemed reasonable to just shorten the straps attached to the hood and lengthen the 'fixed' straps to bring the 'V's up clear of the boot cover. However, in playing with the positioning it became clear that original anchor point isn't optimal - tensioning the 'vertical' strap in line with the roll bar tube is fine until tensioning the 'angled' strap pulls it sideways, away from the best position to pass through the boot cover aperture.
Moving the anchor point sideways pulls the strap across and very neatly into place, but requires a different fixing method. A pair of 27mm long hex spacers, tapped 5/16"UNF to replace the existing nuts, form horizontal pegs to the side of the rollbar brackets that the modified straps can loop around. A short bolt and nylon washer in the other end helps to stop the strap loop falling off when not in use, although they can be slipped off quite easily if desired.
The rear section of the doubled strap is cut just below the 'V' and a press stud fitted to the loose end to create a new loop when clipped to the existing male stud. (All cut ends were heatsealed using a cigaretter lighter.) It wasn't obvious whether the studs would remain connected under duress, but it hasn't been a problem so far.
The free ends of the upper straps are now too long but can be looped in place and held with pieces of Velcro. They may be cut shorter in the future but it all seemed a bit too final... The straps now pass through the boot cover quite neatly.