OK, I've tried a few suggestions, scrubbing bubbles, fantastic, formula 409, etc.
All seem to work well. My problem was that I was having way too much fun flying and not enough
time cleaning the belly. Obviously with the more hours that go by, crud builds up and is more
of a chore to remove....
So Ben Franklin had it right all along....'a stitch in time saves nine'.

My guess is that every 3-5hrs should be about right.

Angier Ames
N4ZQ