On down shifting, you need to blip the throttle when double clutching.I tried double clutching, only helped a tad sometimes. I have not tried to raise the rpms, I can give that a try.
How would i differentiate between a bad shift key or a bad syncro?
Anyone have any pics of either part?
Sometimes it is enough just to blip the throttle as you pass through neutral without raising the clutch, since there might be enough drag on the clutch disk to let you spin the input shaft a little faster.
Going uphill (up shifting) you do not need to blip when double clutching.
This will solve the problem and in general puts less strain on synchros.