ok so i picked up a 5k this weekend and the guy tells me that the head has been decked and so the motor has prity high compression. which should be good but when i pulled the head off tonight i had a look and the two small cut outs on the under side of the head which you can usually use to lever it of are prity well gone! you can still see them but only just feel them with your finger nail. how much have other people decked these heads in the past and still had success? without pingging all the time?