Large crown / ceiling gap
I know that this topic has been beaten pretty well, but wanted to get some more specific advice. I am installing white crown in a guest bedroom of a 100 year old condo with plaster ceilings and walls. Everything is wavy and out of square, to say the least. Three of four walls ended up darn good, with pretty minimal gaps (nothing greater than 1/4 inch), but one wall has a gap of about 5/8 inch over about 2 or 3 feet. I've read that the most sound way to fix this would be to float the ceiling and close the gap, but I unfortunately don't have the time or the patience to do that right now. My wife is about a week past her due date, and wants this done!
The wall is the least looked at in the room, so I'm not terribly worried about the aesthetics. Here's my current plan, please help guide me where I go astray.
1) Find something to fill in behind the crown with the large gap (I'm thinking something light, that would go up almost to the face of the crown, which would provide some sort of backing. Any suggestions?)
2) Fill with MH ready patch
3) Paint ceiling and crown with same flat white to reduce noticeability.
4) Move away soon and hope that it lasts ok for the next owner.
The final part of this is that we're moving in May for my job, so while I don't want to do crappy work, I'm not retiring in this house and looking at it every day.
Any suggestions are appreciated. I'm a fairly handy guy but I don't have a ton of experience and I feel like 90% of the time I'm just winging it!
Thanks everyone (my wife thanks you too).