Look at the back of the seat. There's two sets of mounting holes for the seat bracket. If you are using the upper ones then the booms pulled out. To reset the boom, move the seat bracket to the lower set of holes. This will let you pull the boom in around 6" (I think it's around that distance) so the mesh seat will be a straight swop. I did it the otherway when I first fitted a hardshell seat. Ps. You will have to shorten the chain and all the back cables as well. But that's easier than lengthening them. For a secondhand seat, you could try Kevin at Dtek, Little Thetford. He's got all types of second hand bikes and parts.