Was taught 1.3 Vs by Mike Valentine during my abinitio on gliders. His words were 1.3 will work for just about any aeroplane, remember it.
Over the years flying with different pilots in unfamilliar aeroplanes, watching them and doing the calculation mentally, i've always found the number to be pretty close to what they fly, and also pretty close to most POH's on types i have flown.
There is always the exception of blokes on bonza's 100 knots over the fence, or some others I know, combat power till the crunch.