B737 manual throttle approach speeds and over-run risk management
Landing over-runs are often caused by excess speed above the published Vref. The B737 FCTM advises increasing Vref by half the steady headwind component and all of the gust when using manual throttle. If the auto-throttle is engaged the recommended approach speed is Vref plus five knots minimum. Boeing also recommend that if a manually flown approach is made the auto-throttle should be switched off.
On occasions the expected gusts or lulls do not occur and as a result excess speed is maintained until touch down with the resultant risks depending on runway conditions.
Where landing length or runway conditions are critical and auto-land not available, then would it be correct to say you can legally leave the autothrottle engaged to 50 feet while flying manually and thus use Vref plus 5 knots regardless of the requirement to add half the HW component and all the gust if conducting a manual throttle approach.
If you have got the aircraft to 50 feet safely without additives (by using the auto-throttle), then this would surely minimise the risk of over-runs associated with excess over the fence speed?