As I understand it the draing plug (renewable) is magnetic anyway. Otherwise a magnetic one is fine. Mrs A's Octavia has a full undertray for the front which is flatter than the one in the ad. But if yours does not have one that seems reasonable.
I would get some miles in standard condition first. Make sure you know what technique works the best. Air con vs windows depends on the car. The air con in the Octavia (same as yours) makes no noticeable difference to performance in my experience. I left it in Auto mode for a month and Mrs A didn't notice.
EDIT - this is in the wrong thread - move along, nothing to see
