about vhdl code for cic interpolation filter

I implemented a CIC interpolator with Quartus CIC compiler and it uses one bit more for each integrator than your design, resulting in equal width of last comb and first integrator (as usually expected) and 49 Bit output width. I must confess that I only CIC implemented decimation filters on my own. Thus I'm not aware of possible errors or ambiguities in Hogenauer's paper related to interpolation filters.