Thanks everyone. Got it all sorted out and installed. A 1 1/4 " shim on the outside of the fan/vent will allow the plastic trim to sit flush with the ceiling. Looks very neat and tidy. Now i dont have that annoying chain hitting me in the face .
The 4 holes in the knob trick worked fine. I did decide to cut i bigger hole in the floor just because i feel it will add good ventilation and will pull cool air from under the RV. The hole will fit a 1 gallon ice cream bucket. I can remove this bucket at will.
I'm always very happy to come up with something that is dual purpose but I must say you've got me beat by a country mile!!
1) drain water
2) prevent wet floor syndrome
3) provide good ventilation
4) pull cool air from under RV
5) make ice cream