Hi Guys, I'm new to the Kawasaki line of PWC and just bought a 2006 STX 15f. Awesome machine, compared to my old 2004 Seadoo GTX. Anyway, I'm looking to install a new impeller and I was told to go with the Solas 14/21 Concord. I noticed there is a 15/21 concord. Which would be better for out of the hole and to maintain my top end. The top end on the speedometer shows 62mph and this machine is stock. Any feedback would be awesome!