I found that v brake plate had quite a bit of flex in it, so i fitted a regular brake booster plate which reduced the flex a lot. Using jubilee clips to fasten it instead of zip ties makes it difference as well.
Its all a bit of a mess though, I would ask around to see how much you can get some mounts brazed on for since its a frame you will keep for a while.
I found that v brake plate had quite a bit of flex in it, so i fitted a regular brake booster plate which reduced the flex a lot. Using jubilee clips to fasten it instead of zip ties makes it difference as well.
Its all a bit of a mess though, I would ask around to see how much you can get some mounts brazed on for since its a frame you will keep for a while.