I'm going to be doing 5gal big beers and 10gal normal beers in a 15gal keg, anyone with experience have an opinion on how the 1/8" diameter difference will impact my cooling time?
Did you ask them if they will build a 1/2" SS chiller. I notice that they sell 1/2" tubing, so worth a shot. Somewhere on HBT someone (Bobby M?) did a comparison of chiller dimensions vs cooling times.