I posted two more, frankly populist questions on the Physics StackExchange site and got good answers. My reputation now stands at 42! (Clare asks wearily "Is it all men on this site?").
First question: "Is there a maximum possible acceleration?"
Second question: "What would happen if a large relativistic object hit the earth?"
Click on the links to see the full questions and the rather interesting answers.
Mundane news: our replacement DVD player arrived today, accompanied by The Brothers Karamazov.