Thimbles For Galvanized Rig

[trofast]

After reading "The Complete Rigger's Apprentice", I decided to splice 1/4" 7x7 galvanized wire for most of the rig on my Cape Dory 28. My knowledge is limited, so I thought I would turn to the community with a couple questions:

It has been suggested to increase the thimble size 1/16" over the wire size. i.e. 1/4" wire = 5/16" thimble. Is this common or good practice?

With galvanized wire, it is my understanding that I will need either galvanized or stainless thimbles. I found these cast, closed end 304 stainless thimbles online. Has anyone used these and will the square bottom be a problem?
http://www.uscargocontrol.com/Riggin...himbles-SS-304

Thanks,
Jonathan Hilbert
Baltimore, MD