Not very scientific, but heres about what I found at my house with great sprint signal (full bars).
2 speed tests right before the change were:
right after step 1:
Did not change the home IP as the secondary IP already matched my closest point. So I figured that meant that it already had the primary correct. Maybe logic is flawed, IDK.
Changing the slot index did not seem to have any effect. If anything is slowed down a bit about ~ 1000 kb/s. But it doesn't seem to affect the incoming call, at least not that I could notice.