Changed config.xml to 1280 720 0 0 blue skin, updated from 01-17-080612-15-POP-402-000 to 01-17-080812-15-POP-402-000 and now it works. Also along the way, I got rid of extra <MVPSpecificSettings> in config.xml.
720 0 0 crops GBPVR menus well on my TV;
<MVPWidth>1236</MVPWidth>
<MVPHeight>712</MVPHeight>
<MVPOffsetX>44</MVPOffsetX>
<MVPOffsetY>8</MVPOffsetY>
looks a lot better
Will I have issues if I change MVPWidth/Height back to 1236/712?
Also, it it worth updating to 01-17-081023-15-POP-402-000?
You can experiment with any screen setting you'd like, however it looked like a skin error was causing your problem at the resolution you had. I don't recall why now but since I asked for you to change to blue, maybe the blue skin will work at the settings you like.
As for firmware, generally it is better to go forward. I am using beta 081218 now! In fact while I think about it, the the instructions in the Dummies guide won't work for the mvpmc share method on the 080612 firmware because of changes that Syabas have made since then.