I don't know what units your 0.75 and 0.3 are in (mm? inches?), but both would be too thick for sure. The best option would be to use stretched sprue, as per Jim Baumann's method, since you can control how thin you want it to be:
viewtopic.php?f=4&t=37536Alternatively, the thinnest commercial product is UNI-Caenis, a fly-tying line. It is just about right for 1/700 scale, so would be too thick for 1/1250 if you were thinking of doing ALL the rigging, but should be fine for your purposes of a few simple strands for representation.