Well, for starters, something like this:

Find a hill, from a standing start, coast down it to a landmark, and time yourself with the cyclocomputer. Try to get 30s in there (if you coast down to 15mph or so, that's fine). Record each time with a pen and paper between runs (label all your rows before the test starts).

Get a baseline time in the drops.

Then try your bars "flat" for one run, tips up 1" for another run, then another 1" up for another run.

Then run all four tests backwards (all the way up, 1" up, flat, then drops).

Then widen or narrow the elbows and do the three aero bar tests again, twice each, in some sort of non-paired order, as before.

Take the two fastest configurations and test them side by side twice (two runs each, alternating runs).

Then see if you can adapt to that position after riding in it a couple times/week (for long stretches) for a couple weeks.