Thats real slick, I was getting ready to do the same thing over spring break... I bought some 1/2" square AL cause I figured that would make better contact on the sides... got some 1/2 brass barbs that just fit in the ends, figured with some jbweld it would work well.
Tho then when I started to think about it I don't wnat to use AL and can't find square copper anywhere around here.
Anyways that looks real nice, and I'm going to worry less... my goal was withing 5C of watertemp and i was thiking that was unrealistic but good to see its not
Nice job.