Most barrel heads are not charred. Only Woodford chars the heads, so far as I know. Therefore, head contact is of little consequence regardless of the orientation of the barrels.
Don't lose sight of the fact that no more than 5% of Beam's whiskey has ever come from palletized warehouses (my estimate).
The palletized warehouses were new when I saw them in 1991-92. So far as I know there were never more than two of them and also so far as I know, they are still in use.
Since we're all making assumptions, I assume the maturation experts at Beam would have made every possible adjustment to ensure aging consistent with their flavor profile. That would have been job one and that part of the experiment would have concluded by the mid-90s.
In Beam's case, I believe the palletized warehouse was a reaction to the decline of the labor-intensive practice of barrel rotation. Much like Jack Daniel's and Maker's Mark, and unlike Heaven Hill and Buffalo Trace, because so much of Beam's output is in one expression maturation uniformity is a very high priority.
The palletized warehouse was, due to the forced air circulation, an effort to ensure more uniform maturation. The use of pallets and fork lifts was also a way to move barrels around within the warehouse in a more cost-effective way.
If they found that the palletized warehouses took 20% more time, that meant that with the addition of that time, the result would be the same, hence undetectible, hence that fact is of little consequence in this discussion.
All that said, I wouldn't be surprised if leakage was a reason for deeming the experiment a failure, but less than optimal maturation might also be a reason but they choose not to reveal it, which would be a very Beam thing to do (or not do).
However, if the results were really unsatisfactory, they would have stopped using those warehouses years ago and moved the barrels into rackhouses. It was my understanding that they weren't going to build more of them but they were going to keep using the ones they have. Presumably they're also still trying to tweak them.
So I think you're chasing nothing if you think you can taste the palletized whiskey in any Beam releases. Unless they do an all-palletized release, this discussion is moot.