Currently shooting 700 Dark Timbers cut 30 inches with 250 up front from my 38@28 Kanati longbow.  I draw 27.5 inches and shooting a B55 string.  I really wanted to pick up some 1916 Autumn Orange shafts to fletch up.  Do you think if I leave the 1916's at 30 inches that they will shoot out of my bow or do I need an 1816 shaft?  Really wanted orange. 

With that much weight up front and left long, 1916s should work. You may need to do a little tinkering to get the best length.  Doubt they'll seem stiff, but if they are, a low stretch string would solve the problem. 

1816 is 44# spine at 28"

1916 is 52/53# spine at 28"