Bill, my first cobra had the bungy deal for the boot and it worked a treat. Was firm but not tight and never bounced.
Now as far as giving up DON'T! I watched your 40 being built, tried in vain to buy it after it arrived and now one of Australia's richest men own it (Tony Denny) I have tried to buy it off him a few times without success. He wants ALOT for it so he knows how good you build your cars.
Keep going....it'll be worth it and you have many a build admirer downunder! Have a break and revisit it mate.