I have never done the model monchit...but here are some links that should help you..
http://www.army-technology.com/projects/challenger2/
http://www.fprado.com/armorsite/chall2.htm
http://www.mod.uk/dpa/projects/challenger.htm
http://www.deathorglory.com/cr2.htm
http://www.geocities.com/SiliconValley/Lakes/3457/chall2.htm
Hope it helps..
Cheers
Rob