I beleieve that 8 strnads is enough for the draw weight, but I always make strings at least 10 strand, and most common 12 strand. I make many strings for Boy Scout and Church Camp archery programs. I am not as worried about the string noch wear as the difficulty on the shooters fingers and keeping an arrow nocked on the string if it is too thin. I also use two wraps (4 extras strands) in the loop to give the string more longevity. That way a ten strand string will have 9 strands in the loop. The strands do bulge a bit where they 'Y' back together, but I feather the length so it makes a smooth transistion.
A bow of that weight is not going to be shot for a great distance, and probably by a younger person, so I do not worry that the string will effect the cast by causing a lot of extra drag.