The seat tube angle on the LHT is fairly slack, and I've never really liked the way the Carradice hung from the bag loops on my saddle because of it. Last week, I finally got around to doing something about it.I cut a short length of pvc pipe, wide enough to feed the seatpost strap through.
Then, I cut a longer piece from a 26 x 2.00 innertube - this went through the pipe, with the ends folded back over the outside, and taped down with electrical tape. The tube should, I hope, stop the pipe abrading the bag.
The whole lot goes over the seatpost strap, and stands the bag a little way away from the post.
With something reasonably firm packed against the seatpost end of the bag (a book, for example), the bag now hangs at a far better angle. As a bonus, I finally feel like a proper Carradice owner, having used a few pennies worth of leftover DIY stuff to fettle the bag.