I've got a rental coming up where the KLM code is cheapest. If I book a compact and add an upgrade coupon to midsize, it saves me a few dollars. But it also converts the reservation from Emerald Aisle to Counter. If I take out the coupon and book a midsize, I have to pay a few bucks more and I get Emerald Aisle. This seems absurd, but that's how the computer prices it. I called Emerald Aisle reservations (kind of felt like 1998!), but they couldn't fix it.

As a practical matter, does it matter? Could I just book the compact, go to the Emerald Aisle and then tell the guy at the exit booth what I'm doing?