I understood what you said but I repeat once again this is not Brian Green's opinion
I translate from the "factory of cosmos"

"If the strings were 10^-18 mt long , the mass of the particles which corrispond to the highest frequency vibrations would be hundreds or thousands protonic mass.
This energy level will be available when the new particle accelerator LHC at CERN is ready "

P.S

Before 1996 the dimensions of the strings were supposed to be about 10^-33 cm
if so no test would be possible ,the amount of energy being enormous