antenna suggestions for Bowling Green, FL

[rca]

We are snowbirds spending the winter months on Hwy 17N (zip 33834) between Wauchula and Bowling Green, FL. When we were in the area last year, we couldn't get the CBS stations chnl 10 Tampa Bay or 11 Fort Meyers consistantly using the Winegard batwing w/ digital booster attachment. Can anyone suggest a small, light weight OTA antenna that I can use to pull either of the channels in? Any of the ones I've looked up so far are huge. I plan to mount it on a ten foot long piece of 1" steel conduit bracketed to my roof access ladder on the rear of my class A motorhome so it will be about 18 feet from the ground. Thanks!