I am not sure why everyone is arguing about this stuff on this thread. As I read each persons response I am in agreement with them all. Yes, some people get more technical then others about how the system works, ie: weight transfer and the like, yet I believe we are all in agreement.
Balance is the key!!! To remove the stock proportioning valve without an improvement to the rears throws the balance off. The stock system is balanced so to speak with the valve in place.
If the valve is removed, the brake system should have some upgrades to bring it back into balance. Without going into the gnats ass detail on the braking system design, I believe we can sum up this thread by saying that we all agree the key to brake system performance is balance!