The wire or line going slack on the side with no tension will not hurt a thing.

As to the correct line to use, make sure you use a fishing line product called "Braided Spectra". The example given earlier of the brand name "SpiderWire" is braided spectra.

This line has practically zero stretch. If any slack appears, it is usually because the fuselage itself expanded or contracted due to temperature changes. It is good stuff. Be sure to us a drop of CA on knots as this line is slippery and difficult to tie without the knot slipping.

Tom