I'll keep a long-ish story short: I've got the screws that attach the hanger to the dropout stuck in the dropout. I was able to get the hanger off with a dremmel but screws are stuck. Are those holes in the dropout threaded? I think it will affect how I get those screws out i.e. drilling them out vs a screw removal type device. For reference, this is a cervelo s5, the dropouts are carbon. For those not familiar with this frame, the screws pass through the dropout from the wheel side to the outside and screw into the hanger.