We couldn't resist, we just had to put a multi along here somewhere.
When you get to GZ you will see a sign - it's pretty obvious. From this sign you will need to answer the following questions.
A = How many rabbits are on the sign?
B = How many letters in first line?
C = How many 'screws' hold the sign up?
D = Add together rabbits plus screws plus amount of letters in 2nd line
Final is at S42 51.DCB E170 50.BAC
Check sum = D+C+B+B+A+C = 19
At final GZ there is a fairly obvious spot. Cache is a bison so own pen required. Ensure it is well hidden when replaced so it can't bee seen from the track in either direction.