Nargott
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It's simple: Tier 6 units can only be recruited from a Castle, meaning if the base recruitment rate is 1, the maximum is 2 (1-2).
Regarding farms, yes, a +200% bonus might not be suitable in all cases. Either we make it +100% for some (which wouldn't match the tier and building level), or we don't return all farms, but only the low-level ones.