I think you might have that reversed 26" tire would be 3.55 while 27" tire would be 3.23. A taller tire would equate to a lower numerically or taller rear end ratio.
Otherwise, you bring up an excellent point. Assuming you have the room making changes to tire height can play an important role in tuning. Thus if you wish to go through the traps near redline in fourth gear you can tailor your speed with a change of 1"- 2" in tire height.
One other thing to consider. Given two tires with the same width, the taller tire has a larger contact patch. So if you reduce your tire height from 28" to 26" to put a little more gear in your car, you could end up with a traction problem because of the smaller contact patch. You might erroneously believe that your new found traction problem is because of the now lower effective gear ratio when the smaller contact patch might be the culprit.
You can play around with different tire and final drive ratios here:
