Hi Skip
While I just celebrated a birthday I HATE to think of myself as an "old timer"!  However, I looked up the Shark magazine article and it strongly "hints" that Lew used 70's for his Shark.  Your 69.5' handle to centerline sounds legit but be mindful that cable lines will stretch over time and you might someday soon end up over 70'.

I have flown Big Sharks, launched them, and seen plenty of them fly. 69-70 feet C. to C. is the way to go.

Remember, the K&B 45 seemed like a monster compared to the usual Fox 35 Stunt.  But it's not all that much compared to the stunt engines of today.

Lew probably used 70's due to the preceived power, weight and line pull back in the day.

What you described is pretty close to about 68 feet C. to C. About right in the ballpark. You should get used to measuring your lines from the center line of the plane, to the center line of your handle. Those are the distances that actually count in competition.

Regarding line lengths, the only thing that "counts" in PA competition is the minimum of 25 feet and the maximum of 70 feet, "measured from the center point of the grip part of the control handle to the fore and aft center line of the model."  Many stunt fliers refer to the length of their lines measured from eyelet to eyelet, knowing that there is a 70 foot limit as defined above.

Keith