Uhuh, same thing happened to me on my echo. Being an engineering student, I had access to the workshops, and I re-drilled the mounts to 5.5mm, then tapped to M6. Then I had to mill the slots on the clamps to 6mm. Now all four mounts are using M6 bolts, which are much stiffer! As in, the bolts are stiffer than the M5 ones. I used a hand drill at first, to drill the mounts on the frame. Unfortunately the drill bit broke, but I managed to take it out. Best is to ask a friend over to help you hold the frame on the drilling machine. The drilling machine is way better, faster too.