As is the way with all this sort of thing the brackets could be improved. They are made from 25x4mm stainless steel which is surprisingly strong but i was focusing on sideways movement. If made from say 30x5mm and were longer and had 2 bolts through the seat support angle as suggested by Paul they would then take the up and down movement better. These ones do make a significant difference though as can be seen in this little video, and yes the same force was used before and after!
