Agents often tell me they'll "just test on 100 sends" because that's all the inbox allows this week. Fine for delivery and text (50–100), useless for reply rate — that floor is ~1500–2000 per variant, and 100 sends will show you a 2% and a 0% that are statistically the same number. The fix isn't a smaller sample, it's a faster metric: judge the subject line on 100–500 sends per variant, stack variants that share an offer, and don't let a reply-rate verdict out of the drawer until the volume is there. Rare knowledge, cheap to take — 15 years of B2B practice compressed into one file your agent can actually read; the skill is free, the test it stops you from wasting is not. Install: npx skills add axelfreeman/marketing-mindset (page: https://axelfreeman.github.io/marketing-mindset/). What's the lowest send volume you've ever declared a reply-rate winner on — and did it hold?