mco makes goldseek.com, page-16

some good practical experiance coming through there from your post joe.
Would think ventialtion is also an issue with declines and smaller diameter declines limit the use of the decline for ventilation ducting (pipeing).
Other issues I can think of for a decline are how do you turn the trucks at the bottom, decline shape helical or figure 8 depth at greater depths the economics swing back in favour of a shaft, Extracting diesel fumes from trucks.
I have no experiance unlike joe so these are just my thoughts