When your ripping boards, don't cut it all the way though, leave a little hinge wood so the log stays together then finish each cut quickly at the end.
Also the logs it's sitting on, I just cut a V out of it to allow the log your milling to sit in and I use the V as a wedge on the ground keep keep em from moving around.
Sorta random but i noticed your from london.....if you go for a hike in the caines woods area you will find some really old big stunts that have rotted and fallen over. I built those back in 97'-98'.