Has anyone experimented with omni directional antennas mounted fairly high?

I am thinking of mounting one of those round, amplified omni directional antennas on the top of the mast at 70ft. I am not expecting it to act like a larger antenna so I will also be adding a directional antenna under it.
Here is what I am thinking.

I am 60 miles on average from the majority of stations which are not in one direction, but all around me.
I will put a Channel Master CM 4228 - 8-bay bowtie at around 68 feet with a cm 7777 preamp, and a coax a bit better spec than RG-11 (existing setup), and then install the Winegard MS2000 Metrostar Omnidirectional on top of the mast with either RG-11 or RG-6

My question is, has anyone heard of how the winegard will perform picking up DTV at that distance on UHF, keeping in mind it is up 70feet?

I intend on possibly having the ability of connecting the two together and switch out the winegard if the multi path gets too bad, but if I do have to rotate the antenna, other people in the house watching the winegard won't loose the signal.

I plan on doing this soon as I have to replace a wind damaged antenna, and I just don't want to put up the huge VHF-lo antenna since all those channels will be disappearing next year.

I spoke to the Canadian counterpart to the FCC, and they don't plan on shutting off any analog stations in the near future. He said there is no set date and have a wait and see attitude following the U.S.

Those things aren't generally rated for more than 30-35 miles. Good luck.

I did a little research on UHF omnidirectional antennas and I can't help but conclude that the Winegard must be an extreme compromise. To cover that frequency range, have a true omnidirectional pattern, and be efficient in such a small package is essentially impossible. No wonder they say "For use close to the transmitter."

I did run across an interesting antenna that looks like it could be designed to cover channels 14 - 51 and be a decent performer: the Turnstile Batwing. See photo here:

http://www.qsl.net/kd2bd/batwing.html

It would take someone who knows what they're doing with antenna modeling software to get a design that would actually work and then someone who could build it.

Chuck