I've got some 18" 'ultra light" 330 gr. arrows coming for friends Vixen. They are reported to get about 290-295 fps. They will be the same as my GT LII's except for weight and length. I'll be checking them out for accuracy and helping him sight his scope in, so hope to have some things to share on the subject. I personally don't think that much difference in length will affect much, but the weight might.