The F53 is know for a harsh ride. Supposedly the newer versions are much better, but maybe not enough to make a difference. One thing you have working against you is that you have a shorter chassis, which means less weight. It could very well be that your suspension is designed for a much longer, heavier coach. According to other F53 owners who have posted here, better shocks will help. Secondly, I would look into something like Morryde or Sulastic spring shackles. Sulastic may not list the F53, but last time I talked to them, they were willing to make anything. Sulastic will be fairly inexpensive compared to other solutions.