Many people bad mouth in mast furling but it is usually due to ignorance. I was skeptical until I got a boat with a furling main a few years ago. Many will say it jams but any jamming is usually due to operator error.
Here's the proper way to do it. Ease the main sheet, ease the vang, grind the outhaul while keeping tension on the furling line. The most important part is furling the main. Most problems arise from improper furling. To furl, ease the main, ease the vang, grind the furling line while keeping tension on the outhaul. Keeping tension on the outhaul while furling is important. If there is no tension wrinkles will occur. Keep an eye on the sail as you furl, if it wrinkles haul it out a bit and try again. Yes that is a 393 in my avatar.
If you want more info on the 393 try here:http://groups.yahoo.com/group/beneteau393/
beneteau393 : Beneteau393 Group
As for chain it depends on the company but I would want a minimum of 200 ft.