I've had the HellFire 510 for a while now and love it. I am around 85kgs and initially I had a plastic quad set (not sure what they were) which was just ok then I got a set of fiberglass Stretch quads which are medium in size and that was a little better. I didn't like the feel of the plastic or Stretch quad fins as they were too small I worked out. I am 85kgs (190pounds i think) and since I change to the fiberglass SA4 (Simon Anderson) large quads its been a game changer for me and that board and I am so stoked on it. It goes to show changing fins around is very important if something is not right.