Ah. If the fwd limit is different then although it's the same wing the stall speeds WHEN CORRECTED TO FWD CG will be different - higher on the -800 with a further forward limit. A delta of 3% on cg doesn't sound big enough, though, to justify the speed changes seen, though - 9knots on V2 would be something like 7 knots on stall speed - not credible for a 3% cg shift.