i don't rely on blue tape anymore.  "frog tape" is the best product i've used for crisp lines.  it's green and the directions say to moisten it prior to painting.  it "shrink wraps" itself to the surface yet is easily removed.  it's available at the big box stores, a little pricey but isn't everything that works... 

p.s. worked great on my wd10 fiberglass deck over-wrap too 

Thanks...that sounds promising...I will raise up the water line 1/4" and try the "frog"...the wife says i should work out all these little problems before I build hers...I didn't know I was building her one ?!

Hey Dan...   Another thought is 3M Fine Line tape.  I used that on my Wood Duck 12 , with an epoxy/graphite bottom & it came out VERY well. I just tacked down the paint edge so it also came off when the bottom coating was finished and still tacky.   Another thing; I first applied the tape to match the wire "holes".  Once painted, I thought it looked funny.  So, on the second coat, I started at the wire holes but at the middle, I was up about 2 plus inches.  Good luck and WELCOME to the quacker fleet....   ~BRUCE~