Stripped the old insulation, after measuring the positions of the cut-outs for the carbs and the rad. These will have to be cut in the new insulation as there are no pre-cut pieces for the V8, not even for 77 and later 4-cylinder cars with the radiator in the V8 position. The material had shrunk quite a bit, and looked a lot rattier lying on the ground compared to lifting the bonnet when fitted.
The carb cut-outs had moved quite a bit, as can be seen from the rub-marks from the damper caps, and the damage to the edges of the holes when the near-side engine mount rubber had broken and the engine was tilting under acceleration.
The pieces came off in one lump with the aid of a scraper, leaving basically just the adhesive behind. More scraping got all of that off, took about 90 minutes all together.
New pieces trial fitted - 5-7mm short all round. If they had been made that bit bigger the edges would have tucked under the bracing pieces and wouldn't tend to peel up. The ones I fitted to the roadster 27 years ago were the same, but I wedged strips of lath under the strengtheners and over the edges of the material while it was drying, and they haven't moved since. Next question - how to cut neat circular holes in the new material!
Pondering cutting the circular holes in the rear piece of bonnet soundproofing I hunted around for something about 6cm in diameter, hoping to find a section of pipe I could use to cut the hole. But the closest I could get was an old V8 engine mount rubber which was 6.5cm. I cut a test hole on the old soundproofing, drawing a pencil line round the mount rubber, then using the point of a craft knife to pierce it closely spaced all the way round, then carefully pulled the knife through the piercings to join them all up. That turned out well.
As I had nothing of 6cm I could draw round I opted for sticking strips of masking tape onto the new soundproofing, measured and marked out the centres, then drew circles with the compass from a set of mathematical instruments I had been given on progressing to 'big school' at age 11. The measurements for the carb cut-outs are critical. I had the old soundproofing, and I also found these from the V8 Register. The measurements tallied, including 6cm from the edge to the 'top' of the holes i.e. 9cm to the centre of the 6cm holes. However you can see from the old soundproofing and rub-marks on the bonnet that they were positioned too far forwards - being more like 7cm on mine, as well as a little off-centre, but I settled for 8cm and kept them centred.
Cut as before, and was pleased with the result.
The rectangular cut-out in the front section - is it needed? The filler plug is easily 1/2" higher than the highest part of the header tank, and as that is twice the thickness of the soundproofing, strictly speaking one only needs another circle for the filler plug - if anything at all.
In the event no cut-out there is required. With a cone of 'Pritt-Tak' stuck onto the highest part of the header tank, and the bonnet pressed down carefully until it just latches, you can see at least 4mm clearance to the highest part of the plug. In fact it is even more than that. Unfortunately the insulation hasn't completely stuck in the central areas, including above the plug. And using a retracting tape measure on the ground, projecting up immediately behind the radiator until it just touches the insulation, I get a similar clearance. But if I then lift the tape measure up, lifting the insulation with it, I get even more clearance. That's slightly optimistic, as with the tape behind the rad, and the upward slope of the bonnet panel and insulation, I'm getting slightly more than is directly above the plug. Having said that the Pritt-Tak is slightly pessimistic, as the bonnet and insulation are slightly getting lower towards the sides of the bonnet.