How do you guys find enough iron for projects like this 
It's like...every two iron deposits you find will only give you 16 tiles worth of rail. Is there even enough iron in the ground to make a rail from one spot to a place in the horizon?
You'd be suprised, if you stop ignoring the odd peice while you explore, your iron qauntities go through the roof. Least, if you find a monster cavern.
To be honest the biggest problem I've had this map isn't iron supply, its actually having enough cobblestone and gravel, as thats what the tower is mostly built of. I just upgraded it now and its double decked now (under the large section is now an identical section, doubling its productivity) at a guess, it probably cost in the region of 640 cobblestone, 320 gravel and another 320 dirt, because I ran out of gravel but had enough dirt on me to finish the job :V
was totally worth it. The productivity has definately doubled. If only I had some sand I could make 4 TNT now, and I'm nearly fully stocked on arrows
EDIT : got a
screenshot before I picked up all the stuff this time around. Its working well...