Lucky you, would love mine to be 1.58kg. I used to run a Nobby Nic 2.4" on the rear which was 650g. Must have had around 20-30 snakebites in a month, after that i threw it away. It was the most awful, pinch happy tyre ever. Surely this Conti can't be any better seeing as it's actually lighter. Also about the stiffness, have you tried removing the booster? When I got my frame it was flexy as f**k, brake wouldn't work at all. Even an Echo 4 bolt booster couldn't keep it from bending. After a few weeks of riding the brake started becoming more and more solid up to the point where the booster was no longer necessary. Now the brake is pretty much rock solid.