michbill wrote:
...we have only spent about 10 weeks in FL near the Atlantic Ocean...
That may have been enough. I spend winters next to the Gulf in a high salt area. You can get away with 4 weeks, but much after that and you're going to see issues.
Without seeing the amount of rust you have, it's hard to make a conclusion. FWIW, I spray the whole underside with ATF fluid from a dollar store spray bottle. Just make sure you keep it away from hot areas since ATF is flammable. Works well for me.
Another option that some feel is better is the use of
Fluid Film.