I'm currently working on a kite-sailer ( see: http://www.kite-sailer.com ) and the kite control bar requires thinner lines - for initial testing we used sailing lines as I'm mostly boat-builder / sailor but they are just plain simple to bulky to make it work smooth.
Comparing the tensile strength of different products - dyneema SK75-12 lines have the best diameter to breaking strength numbers ...
Avg. Tensile strength for 1.8 mm - 1000 lbs
Avg. Tensile strength for 2mm - 920 lbs
Avg. Tensile strength for 3mm - 1920 lbs
With a price of average 0.45 per linear foot.
Available kite lines have Dyneema fibers as well - just not sure if 65 or 75 - their description is :
"PKS High-Visibility Pro-Lines line sets are high quality Dyneema lines specifically designed for kite-boarding, with a 700 lbs test strength .... at 0.54 per linear foot"
The kite lines I bought recently have 1.6 to 1.8mm cross section - the sailing lines are treated against UV and are often used for lifelines or running rigging where they are exposed to UV on a 24/7 basis ...so just wonder what might be the difference on the Dyneema SK75-12 to the kite lines?
Other aspect of interest is with a increase of 1.2mm line diameter - you could increase the breaking strength by more than 100% - and have a better overall line ---
Is the small diameter so important? Or am I missing something?
Michael

for a kite 3mm seems huge, but it depends on the size of the kite i guess....

3mm is equal to 1/8" and the lines I just bought are 1.8mm ( just a bit more than 1/16 ) - so we just increase by 1.2mm ( 1/64")?
What are the disadvantages of this increase ?

drag, weight, cost, pain in the ass.
But, if you need the strength, you need the strength....
Depends on the kite, the load on it, and how it's controlled....

If you can, have a look at Liros lines... IIRC they're thin for their load limits relative to dyneema etc.

Thanks Kamikuza - will look into it
Michael

Some usefull info for you maybe it will suit your application. Have not been able to find Vectran under 3mm though, HMA have not checked.

http://www.performancedesigns.com/hma.asp

The best kite lines are in fact dyneema sk75, though some kite line manufacturers use spectra, call the manufacturer just to be sure.

@JMF thanks for the info - appears as Vectran and Dyneema have the same breaking strength ... need to research a bit deeper to find other pro or cons for one or the other one - but thanks for the info -
Michael

@edt - Just working on the best solution for the lines at the handle bar - as such not a manufacturer question - more best product for the application - thanks for the help.
Michael