As far i know, Until and unless there is a specific requirement which demands to show arrears in another wage type, There is no point of modifying IN42,IN43,IN44 Since SAP has already come up with a design where arrears will calculate with the help of /551,/552,/559.
Now we want to show the arrears for individual wage type then need to maintain payslip parameters and need to maintain wage type in windows with required indicator then accordingly it prints the values on payslip with arrears.
The approach will get varies depends on the requirement and utilization of system.
Regards
Venkatesh