You do not have to CATS or any other time sheet.
Negative time recording can be used for hourly wage earners also. Usually for such employees, a different employee group or subgroup is used.
However if a new EG or ESG can be quite a significant effort for config/testing/implementation as well as for maintenance support.
In such cases, if the number of such employees is small, and if there is no other requirement such as leave accrual, etc which is different, alternative solutions are: using a new contract type, or pay scale area.
In time eval both of these can be used in PCR's to create a new proc type for time w/t generation in GWT function or by using ADDZL.
Overtime can be generated based on the difference between actual att. hrs recorded in IT 2002 and the normal DWS hr for the day (HRS=S gives standard dws hrs after any substitution).
The new pay scale area can be used for hourly rate.