Dave
I am where your at also. The only difference is ..I am going to make my own fairing. I have had some previous experience with fiberglass and feel I can get a custom job that will fit and look as good or better than the other brands.
With that said there are a number of things you can do to get a good fit. But first I would need to know what system you will use to take the fairings on and off. I would suppose that you are going to use the aft trailing edge unfiberglassed and thus be able to just pull the fairing forward to release it's position. If that is the case you will need to rework the trailing edge of the fairing to close the gap you have. Major fiberglass surgery to the extreme or heat gun as a minimum. You will also be adding screws in some strategic locations to hold the fairing to the wheel pant. this would also help close the gap. With this all said if I were there at your side my suggestions might change ......especially being able to see all sides of the problem. At any rate fiberglass like the metal parts of the plane takes patiences, a dose of ingenuity, and an expectation of doing the best you can to get the job done.
My fairings will have the trailing edge closed, will be fiberglassed to the wheel pant, and cut along the same line as the forward and aft sections of the wheel pant. That way when the forward section of the pant is taken off the forward section of the faring will just come along, attached....ditto for the aft. I would do the same with your fairing if it were me.... but ..... as always your milage may vary.
Frank @ sgu and slc.....RV7A