Chosing polyphase interpolation coefficients
At Peter K's suggestion I am submitting my solution as the answer. In the poly phase filter the 9 coefficients were all symmetric about the center but gave poor ripple performance. When arranged in the format of a poly-phase filter the 3 coefficients in the 3 branches did not add up to the same value for all three branches. By making a slight edit to the 1 coefficient at +/-3 positons from the center all the branches added up to the same value and the results are as shown.

To get better performance then that shown I need to increase the # of coefficients to N=15 (wanting to keep N a multiple of L=3 and odd).

Brian