2+1 side biter placement

new project, 6’0’‘x20x 27/8 going to be a center box with small 3’’ 1/2 side biters, single fin placement in box to be aprox 6 1/2 up from pod, fin to be 6.5 high by 5.5 base , but not sure wot to place sidebiters at, at the moment got them at 11’’ 3/4. any help?

Is the 6 1/2" single fin placement the trailing edge? If so, it seems like your fin cluster might be pushed forward a bit for a 6’0". Is it a really rakey fin, or just a standard 6 1/2" fin? Any pics of the board?