Hi Steve
The Sailwave SailNo Entry Wizard allows you to Select the number of digits you want to enter.
So enter the full no of digits into sailwave when setting them up but only enter the last 4 when entering the results. If there are duplicates because the last 4 are not unique then they will be shown in the selection box below. Just down arrow to them and hit enter.
If you want to print list for the recorders or beach in 4 digit order then you can use my SWList program developed for this purpose. It even prints any duplicates in bold to highlight them.
Details are at:-
https://sites.google.com/site/eskdalesite/home/swclist
Jon