Phasing antennas takes a little bit of work. I just "tee-ed" the antennas together (using a BNC T connector) just to see what the two of them would sound like, and hoping that I would get more constructive than destructive signal enhancement. So far so good...but with the correct length coaxial phasing lines I should be able to do a little better.
I am
VERY interested in trying this. I was always curious if one could connect two different types of antennas via some type of splitter to the same scanner in order to get the benefits of both. If I am reading your post correctly, it seems that it can be done and as simply as using a BNC T connector? Are there any pitfalls I should be wary of?
I realize that you stated experimentation is key here but if you don't mind, I would like to learn from your experimenting.

As you know I am on the road 4-5 days every week so time is very valuable to me when I am home.
That mentioned, though, I would still like to try this myself, since I have the same characteristics of a feed (9 miles from airport, cannot get ground aircraft unless they are the big jets, sometimes experience weaker tower, etc) and it seems that this may really be an incredible improvement.
My neighbors are going to hate my antenna farm that is growing on the corner of my house! But then again given what some of them are doing to their backyards, eff 'em. (The next time I move it will be to a farm with 1/2 mile between me and the next house, but that is a story for another day.)