I managed to win a stock A final using the one-way but it was a pain in the ar$e to drive. Very twitchy.
The car is much more stable with the diff, but this is only on a indoor carpet track. I did try it outdoors (tarmac/rubber tyres) and the car was undriveable. Put a diff in and it was OK.
Try it one day in practice, you might like it, personally I have never liked using one ways but some people like running them. Just don't hit the brakes!
