Bought a board from Coffs Harbour last week dimensions 8'4 21 1/2 and 2 2/5 older style gun with a single fin that slides up and down with allen key. I've only been surfing for abit over a month and it seemed to nose dive easilly as there isn't allot of a concave shape. Did i buy a dud? or is it i'm too heavy at 99kg for it.....any info on these types of boards would be appreciated..