I'm playing Focus Hex 1.10 as a cross for any other poly I use in the mains and it's one of the best to be used this way. It holds tension well, keep the stringbed firmness for a much longer time and it's cheap. Also it lets the main strings slide easily through the entire life span.
As other have said, it's a string to be used in very low tensions. I'm stringing it @ 39( mains @ 43 ).
Also, it must be noted that Focus Hex 1.10 is a much lighter string. Even on a 18x20 stringbed and 98" headsize, a full bed of Focus Hex 1.10 weighs only 14g. depending on tension, it also helps in the boardy feel. That's one of the reasons that it must be stung @ lower tensions
3 matched Yonex Ai100 - B5E x Focus Hex 1.18