Alright, I've commenced the next battle, and although I did cut down on the initial forces a bit, it's still even larger than the Battle of Trysil Pass. Here's a list of the forces involved:
Tau Galaxy
Trinaries Beta & Gamma, 231st Mechanized Assault Cluster
Supernovas Alpha & Epsilon, 116th Mechanized Cavalry Cluster
Trinaries Beta & Gamma, 116th Mechanized Cavalry Cluster
Outpost Defenders [Eric Amirault, Aaron Cobb, Lair Seidman]
Taiga Galaxy
1st & 2nd Freemen BattleMech Binaries, 3rd Freemen Cluster
6th & 7th Freemen BattleMech Trinaries, 4th Freemen Cluster
1st Armored Infantry Supernova Binary, 1st Freemen Cluster
2nd Armored Infantry Supernova Binary, 3rd Freemen Cluster
4th Freemen Artillery Trinary, 4th Freemen Cluster