A Few Strange Questions

I'm trying to work out the concept for a mod and had some questions that someone may be able to answer :).

Firstly how long can you get EIDE cables and is there a electronic spec limit to the length? Also how flexible are those rounded EIDE cables?

Secondly what is the diameter of the fan blades in a standard 120mmm fan and what is the clearance between the blades and the inside of the duct/casing? ( I dont have a 120mm fan at the moment and cant really order one for a while so If someone could measure one I would be very grateful :))

Thanks :).