Simplex would take too long and create too large of its own array during solution.

This is what I THINK you are saying:
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Your device is to access a rectangular array of a photo-optic sensor. Its NxN array represents an AREA-INTENSITY mapping of the light beam upon it. You are to sample the array efficiently to detect any X or Y axis offset and affect centering controls of you motors to constantly re-align the receiver?

So you're looking for a center of mass calculation on the NxN area intensity array?

To start with, you can probably toss all the datapoints not along an artificial XY crosshair, there should be enough characterizing data there if N is large enough and the datapoint values are large enough. This doesn't mean that other configurations might prove better, but it immediately chops the amount of data you have to deal with if I've described the problem you are working upon. E-Mail me if you want to discuss this further.

-Jay C. Box
(I just happen to have a Masters in Operations Research: We eat simplex method for breakfast :-)