Another thing sport fliers might benefit from checking out... particularly for smaller engine models.
The new fishing line material available, e.g., brand name Spiderwire and similar (several brands available) is amazing stuff! FAR thinner than Dacron or monofil (less line drag) and much less stretchy. Lighter. Less fussy to live with than single strand metal 0.008" lines. Not cheap on first view (prices for metal lines are even worse!) but spools will make many sets of 40'-50' lines. Several "pull test" ratings available. 15 to 20 lb probably more than covers metric 1/2A (up to .061 cu in modern engines) needs.
CAUTIONS: New techniques for handling, and forming line ends require awareness, practice and effort.
**Proven and safe useful knots are illustrated on at least the Spiderwire packaging.
**DO NOT try to break this line by wrapping it around a finger and pulling - unless you really mean to remove that fingertip!
**Similarly, do not 'roll in' the line under firm tension on a
plastic reel. (Crushing force apparently is additive, so 2 lines taking 30 turns at 15 pounds
could mean
900 pounds crushing force!) (Haven't tested this; don't care to...)
** The lines are a bit hard to tie off to equal lengths (complicated knot procedures, particularly for the most highly recommended
double uni-knot.) Some means of line length adjustment to give a 'comfortable neutral' handle position is necessary.
AMA Competition rules acknowledge this kind of flying line for limited purposes; check the control line section of the rulebook, which is free to access at:
http://www.modelaircraft.org/