Loaded DD-WRT and cranking up the power helped quite a bit. I can walk through my entire house without losing the UMA now. I added the settings above and have a very stable UMA connection. The dd-wrt allows much more QoS customization than the stock...I was able to give my BB's mac full priority over everything else and, for a nice bonus, even increased priority for my Slingbox based on the port it's plugged into.
I used info from here:
Hack Attack: Turn your $60 router into a $600 router