DS II: Combat Walkers

After purchasing some clearance rack Battletech minis,
I set about getting them ready for an upcoming game of
Dirtside.

While going through the rules on walkers, I noted that
the only sizes mentioned are size 1 infantry walkers
and size 4 or 5 combat and transport walkers.

Why not size 2 or 3? Has anyone noted unbalancing
effects from designing combat walkers in sizes 2 and 3?

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