100% true.They need to be at the same height or you'll have "prop wash" which is the downdraft created by one set of propellers adversely affecting the other props.
Thanks for reply..can u please elaborate on what is prop wash..and see my other post.and pics of quadThey need to be at the same height or you'll have "prop wash" which is the downdraft created by one set of propellers adversely affecting the other props.