make sure that the right forge version is installed (you probebly already did this but i doesn't hurt to say)
i also assume since your using the ultimate pack (FTB launcher), make sure you change the forge version in the launcher not installing it normally i had the exact same probelm...it made me feel stupid (also the launcher i think overirdes the jar...like the technic launcher and the modpack.jar
alternatively you can so DW20's modpack, as that has the new version of xycraft...