Tassie Trail

Hi,

I'm looking for some advice on best kit to buy for a trip I'm planning to the Tassie Trail. What is best type of bag for carrying kit, a back pack or under seat bag, I'm going light and have looked at the Carraidice SQR Trax, but all the MTB riders appear to use backpacks. Is this because of weight distribution? Any advice on this for a long ride?

Also what is the best head light to use for night rides?

Lastly has anyone done a ride like this (480KM's) and what sort of preperation did they do to get cycle fit for 6-7 days full riding?

Cheers
Hemsy