Propper lower leg position can be dicey with pistols. The balance factor tends to make people push their knees into weird places (i.e. too far forward).
Try the trick where you hold a 5 or 10 lb dumbell out infront of you. This can help keep your balance forward without pushing the knee past your toe.
Also, in 'Naked Warrior' by Pavel, he reccomends starting with the weak leg.