[Synchro909]

Whether I double declutch on the up shift depends largely on how cold the oil is. I use a quite thick oil so when the car is cold, I change early (cold motor) and it slides straight through like it has synchro. Once it is warm and the oil has thinned, it depends on whether I want a quick change or am prepared to take it easy (my preferred). Double declutch if I need a quick change, single if I'm able to wait.
On the down change, cold oil takes a bigger dose of throttle between gears. I change BEFORE the corner. I was taught that changing while cornering could cause the gearbox to break if you're a bit quick with the clutch and it did the diff no good either. The mantra was: "change down before the corner and power through it." I find the car much easier to control this way, not that I am a boy racer but wet roads after a long dry spell can be slick. NEVER freewheel around a corner, I was taught