Okay, I figured it out. Set up two airplanes last night using this technique, they all match perfectly from low to mid to high rate throws, and there is no noticable difference in speed. I did it like this:

I reset my radio so that everything was at 0 or 100%(subtrims, dual rates, end points, etc.).

I installed the servo's in the tail, and plugged the right half into channel 2, the left half into channel 7. I then set up a programmable mix to slave 7 to 2 with link and trim on. I had to use this screen to reverse one of the servos.

Using a paper protractor with a hole cut out for the servo, I used the subtrim to make sure the servo horn on both servos were exactly 90 degrees from the servo.

Next I used the same protractor and a extra long servo horn to measure the amount of throw on the right servo. I was getting 50 degrees both up and down.

I then measured my left half, I was getting 51.6 degrees up, and 53 degrees down, I then used endpoints to adjust the throw of this servo to 50 degrees to match the other side exactly.

I then set up a dual rate @ 50% to see if the throws would match, at 50% both sides matched perfectly, tryed 20%, still matched, 75%, still a match. Great, now I know my servo's are throwing the exact same amount of throw through there entire range.

I then hooked up the mechanical linkages, and since I knew my servos were perfect, I could focus on making mechanical adjustments to match them(horn placement, etc). This took about 10 minutes to do, and guess what, my elevator halves match perfectly(I use a digital throw meter, they are exact). I was so excited I immediately went to the ailerons to match them the same way, worked flawlessly again. I then went to the other plane I am working on and used the same technique, worked perfectly.

So, if you want to match any surfaces using two servos on two channels, match the servos first using a servo protractor. Then adjust the mechanical linkages accordingly, and you will be rewarded with matching surfaces. I have been fighting these set-ups for a long time now, and am relieved to finally be able to set these up with ease and to get them matching perfectly, not just close. Now... time to go fly this beast.