Rob,
If I'm reading your avatar pic correctly, you have no. 7 in the fleet of which we had no. 8. In over 12 years of cruising, we never had a problem with the pumpout process at the end of a cruise nor needing intermediate pumpouts on a fortnight's cruise with a crew of 4+. At the input end of the system, the principle of "don't put anything down here that's not been eaten first" served us well. I have no memory of any problems - major or minor - in all the time we had the boat.
JCO