I obsess over getting the best cabin when using my miles. Often, fleets are not upgraded and I get OCD over whether my flight will be optimum. Case in point, flying BA 206 MIA-LHR in F on 6/21/2011. Trying to figure out which bird I'll get with or without the new cabin layout. I found the site below very helpful to those of you pondering similar dilemma:

http://ftdashboard.net/dest/mia.htm

However, its all past history. Any thoughts on how to know for sure a week out? Do operations folks at major airliners make this call last minute or is there a pattern to obsess over to try and crack?

Much appreciated in advance.