Bridge Scoring and sacrifice optimization against slam bids?
In duplicate bridge, 6 spades making 6 is 980 not vulnerable, and 7 clubs doubled down 8 not vulnerable (5 tricks made out of 13 contracted) is -2000. With nobody vulnerable, you'd have to make 9 tricks to come out ahead bidding 7 over 6, scoring -800 for down 4.

Not vulnerable, doubled undertricks score accordingly:


-1: -100
-2: -300
-3: -500
-4: -800
-5: -1100
-6: -1400
-7: -1700
-8: -2000


with additional undertricks being worth -300 each.