[aerohead]

here's some considerations:
1) in order to guarantee reliable quanta, you'd be looking at, at least, 40%-scale models.
2) considering the depreciation in the value of the US Dollar between 1990 and now, a single model would run you about $152,000.
3) there are no wind tunnels to my knowledge that will accommodate two models, side-by-side in a test section.
4) you'd be limited to testing each separately, then comparing the data.
5) from the left coast, to the right coast and back is a 6,000-mile trip.
6) at 14-mpg, pulling a two-model trailer, and $3.30/gallon, your fuel would be $1,414.
7) motels would run around $1,680.
8) meals about $840.
9) wind tunnel time, in a rolling-road test section is gonna be $4,000 / hour, times 2, for $8,000.
10) for one person, one 'test', about $ 316, 348.
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11) if you had your two, ($ 304,414) models, and could get them 3-D scanned, and imported into something like AirShaper, you could save a little over $ 3,900 using CFD.
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12) the models would be too large to place side-by-side atop even the first of three flatbed railcars, pushed from behind by a single locomotive, as has been done in the past for 'single' models.
13) The flow interference between the two would 'wreck' the test, and vibration from the rails would probably ruin the load cell null calibration and any subsequent measurements.
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14) if your talking about TVs & TTs tested as a unit together, you've just 'doubled' your expense, and I'm unsure who could even navigate that kind of testing. NASA's Ames Research Center in Palo Alto, California is one of the few tunnels that can handle TV/TT combinations. And you typically need a DARPA grant to even gain access to the facility, the ' world's largest '.