When scheduling LDR, most performance manuals assume a 15kt overspeed with regards to VAT/Vref anyway?
Even if that were so, carrying extra speed just erodes any buffer built in. If you land a bit deeper than planned (say 1800ft in) plus you are a couple knots over your planned speed which has already got ten knots added to it, plus it's wet...it all starts to add up I reckon.
I am going flying tomorrow and when I am PM I will take note of the exact touchdown IAS on a couple sectors and work out what % of VS it is. I'm picking it will be about 1.2VS, maybe but probably not 1.3 .
Cheers,