My new brooder (photos)

Well, last night I got a new brooder . Someone on craigslist had a large rabbit hutch listed for free. I went and picked it up and it's going to work perfect. I am going to wash/clean it today and get it ready for the end of the month. I will have to remove a portion of the roof so I can hang my heat lamp on one side. How many baby chicks do you think I can comfortable fit in there (I don't want to have it over crowded). And how long do you think they need to be in there before having to move them to a larger area? Reason I ask is b/c right now I have 37 eggs in the bator (not sure how many are fertile quite yet), and will have more eggs going in at the end of this week so these eggs will be about a week to 2 weeks behind this first batch. I was originally going to have them in my hay room where the horses hay is at in one section and put a few bales of hay around them for containment. But now since I got this hutch it's going to work great.

I am wondering for the bottom since it has the wire on the bottom I don't want the baby chicks walking on wire. I was planning on putting shaving in but not sure if the shaving will fall thru the bottom. I thought about putting newspaper in the bottom and then the shavings so when I need to clean it all I'd have to do is pull out the newspaper and it would be an easy clean. If anyone has any other suggestions as to a better idea than newspaper to put on the bottom please let me know.