I'm impressed. I'll be carrying around 12kgs on my C2C in March, in a 45L sac, to cope with 12 days on the route, but without any camping gear, so how you get down to 8 to 10kgs with camping gear I have no idea, especially using a 75L sac, must be plenty of room to spare
This is how I've done it: over the last few years I've been through my gear list (which you can find on my website, and there's also a page headed reducing pack weight) again and again, looking hard at each item one by one, and I kept searching online to see if I could find a lighter alternative, within my budget of course.
It's something retired people have the time to do, but I'd also get my laptop out and do it while my wife was watching a boring programme on the television (which was quite often, lol).
There isn't as much room in my pack as you might think, but while some things are bulky they aren't heavy!
I have now reached the point where I can not make any more gains at all, without spending hundreds of pounds which I don't have on lighter tent, ground mat and sleeping bag.