You can't just put additional flights in the 409 legacy missions. So if you still have 409 legacy missions for some of your maps. The best thing to do is to start from scratch and develop a new series for that map. An easier solution would be to browse this site and find some more recent set of QMB missions for those very maps. https://www.sas1946.com/main/index.php/board,75.0.html
Anyway you can simply add the 4 missing flight for each side using FMB to get the missing....
The 409 legacy was because QMB was adapted to read both older 4 flights and newer 8 flights....without the need to convert each 4 flight to the new format....but if these 'll be expanded to 8 flights these 'll run anyway showing the full selectable second page....
I've done this for the WWI Westfront times ago to test possible multiscenarios in the same QMB mission....even if this could work better with player using only fighter/s and the other 7 flight with each a specific of 4 ground attack targets....they could be 4 bomber and 4 fighters , 8 bombers or 8 fighters and you can add your 4 one to the melee....
This way you can have up to 4 different targets areas each QMB mission....