4cm half height tuna can thickness measurements for the Spring-03 Experiments:

From M. Seely's logbook...
Each tuna can was measured at 4 points in May 99.
#1: thicknesses (in mils)=4.75, 4.8, 4.65, 4.8; so the avg=0.00475"
#2: thicknesses (in mils)=4.8, 4.95, 5.05, 4.9; so the avg=0.00493"
#5: thicknesses (in mils)= 4.85, 4.85, 4.70, 4.40; so the avg=0.00470"

Note that #3 leaked, so was replaced with #5 prior to initial cool
down.
Initial cooldown is scheduled for April 3, 2003. 

Loop1=LH2=#1, Loop2=spare=#2, Loop3=LD2=#5

On March 24, 2003 Mike used a vernier to measure the o.d. of the cans
and found 1.580" (plus 3 mils, minus 0).

So the inner diameters of each cell are:
loop1 = 1.571" = 3.989 cm
loop2 = 1.570" = 3.988 cm
loop3 = 1.571" = 3.989 cm

These will have to be verified by cutting open the cans at the end of
the experiment. Until then this is as good as it gets.