I presented the SVU paper...here's a brief summary:

We reviewed about two years of vein mappings with and without tourniquet.  
At our site, the surgeons have established 0.30cm as the minimum for 
adequate vein diameter.  Looking at 665 veins, we found some veins went 
from being too small to adequate (9%) and some veins went from adequate to 
too small (4%). 

On average, tourniquet applied to the upper arm with patient supine only 
makes a difference of 1mm (.01cm) in the forearm and 2mm (.02cm) in the 
upper arm.  

We were able to follow up on 111 patients.  Those with fistulas created with 
dilation of vein to adequate diameter with tourniquet had a success rate of 
35%, while patients who had veins big enough without tourniquet had a 
success rate of 65%.  

We concluded that tourniquet may lead to more autogenous fistula creation, 
however those fistulas have higher failure rates than patients with veins of 
similar diameter without tourniquet.  

Joe, I believe you were looking for references regarding tourniquet use:  
Robbin has written a couple papers on the topic, but other than that I had 
trouble finding hardcore data other than a generic statement that tourniquet 
should be used.  I think we've done it because that's the way it's always been 
done.  
For protocol, try svunet http://www.svunet.org/files/positions/0809-upper-
extrem-vein-map.pdf 
Here's a launching point for papers regarding vein maps:
http://www.fistulafirst.org/Archives/ArchiveCC3.aspx
Good luck!

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