the best way to know if you have an edge on fabric strait is to fallow a single thread all the way down the edge. then you will know you are on grain. if it still looks cooked then the kilt has been sewn incorrectly. in that case the only thing to do is fudge it. if so then it can't really be brout on to grain if its off in the fist place thees factory made kilts are some times off. this is why thy don't cost as much as the hand sewn ones they turn them out pretty fast. if it is off you could alter it but its a lot of work and taking one apart after its been cut and stabilized is a highly skilled bit of alteration
Paul