The Fn5 takes up where the HBOD leaves off, gainwise. I don't think they sound similar in terms of EQing (I've never thought the HBOD sounded particularly 'tweedy'), and so they mate really well when stacking in my experience. There doesn't seem to be any overlap or cancellation of freqs to my ears.
the HoneyBee and the Formula 5 sound great together for me. I had the Formula 5 going into the HB
By turning the nature knob of the HB down below noon, I can dial out some of the excess top end that the F5 gives me with my Strat.
Formula 5 has way more gain on tap than the HB