Uncoated stocks feel wonderful and print honestly, which is another way of saying they print darker, duller and softer than any screen proof suggests.
Proof on the real stock
Digital proofs on coated paper are close to useless for uncoated work. I ask for a wet proof or a drawdown on the final stock before signing off any colour that matters.
Design for the gain
Dot gain on uncoated paper can add fifteen to twenty percent to a tint. Open up fine type, lighten the mid-tones, and avoid large areas of rich black that will mottle.