Monoline control is allowed and used extensively in AMA/USA style Speed, but not allowed in F2A FAI competition, only in FAI record runs. Actually the 2-line "grouped" flying lines with a small syringe cut from injection needles has less resistance aerodynamically.with a small "flap" in the joint, with two thin wires are side by side and the resulting flow over the wires make this a better choice. In FAI Record runs all the records are made this way,The Brits, Ken Morrisey, Paul Easter etc. have the present world records now. I believe.