So far, so good! Got it on the road today for a couple of miles without any parts breaking or falling off. There is an intermittent clicking I haven't figured out, although it may be the chain slipping over the idler pulley (actually two pulleys sandwiched together). It sounds kinda like the crank creaking, but I don't recall that being a problem in the fixie incarnation. I'm REALLY good at forgetting things, however!
Thanks for the advice, especially Peter for the example of using the chain tensioner to carry the idler and placing the smaller gear inboard, which makes this project surprisingly easy.
Here's a video on the workstand. Can you see the ACS freewheel wobbling? I think the body was bored askew!
http://img529.imageshack.us/img529/2416/48423533.mp4
The gearing is a little on the high side with the 52 tooth ring. I should get something like a 48 or 49, but it's a 144 mm BCD crank, so odd sized rings don't exactly litter the ground.