Merging Two Series

Hello. Our club has two club races per month. One at the beginning of the month and the other at the end. I have scored each series separately so I have two files. Some racers and classes sail both days, other classes and racers only sail one of the days. I have tried to merge the two .blw files using the merge feature in Sailwave under the File menu. I am using the first merge choice and saying that sail numbers must match for the merge to work. My results are not turning out well, some of the classes are fine but others only show two boats when they should show five. Any advice would be appreciately! Thank you.