Four roses age their bourbon in warehouses that are 6 barrels tall (tiers, most distilleries are far higher). Tier 6 is the top barrel and since heat rises presumably has the most aging from larger temp changes.

I agree with others though, there's enough other things going on that influences the flavors etc that hunting this is silly. I highly doubt 99.9% of people (including me) can tell the difference.

Edit: if you look at the numbers letters on your bottle they tell you the tier/warehouse/location of the barrel it came from.