I hate engies in SD, becasue alot of people forget the update that was added in the earily days of TF2. Kill the engie destroy the sentry, wile other spies try to sap the sentry then get the engi, all they really need to do, is back stab the engi and they both die. Anyways, SD would be nice on blackmesa, but as I said, SD gets destroyed by campeing engies and become stalemates anyways.