I notice that professional string jobs have crosses that are perfectly straight. My stringer always strings my racquets where the crosses sag down a bit, like a hammock. Is this something to be concerned about. Although i know nothing about stringing it seems like this could be easily fixed if more effort was put into the stringjob. Is it a big ask to ask him to make sure the crosses are straight? Also note that my stringjbos are very low (45lbs).