On the toughness point, I’ve had my frame covered in paint protection film by armourfend. They supply and fit a special film to stop stone chips on cars. It’s working so far on the bike and it’s nearly invisible – you can just see the edges in some lights. It’s only suitable for the frames that don’t have the soft touch finish – mines an older plain carbon one with the hard finish
I’ve used it on several motorbikes to stop the leathers damaging the paint and whilst it wasn’t cheap to do the bike (I did get the frame for a grand though) it’s now very well protected from stones, scrapes etc. You can buy a DIY kit which would be enough for the downtube and a few other areas. It is a bit of a bugger to fit well though – a fair bit of the cost I paid was time to fit it.
They are based just off the A10, north of London and should have kept the design as well so they can set off their cutter machine if anyone else wants theirs doing!
smurf