In the 2015 season, the University of Tennessee did testing as to get better results in suppressing pigweed (Palmar Amaranth) in broadcast and row crops. The initial findings show using a dual-body with two tips spraying straight down to target made significant gains over traditional single tip or angled application.
[Update for Feb 23, 2017]
For the abstract of the test and article, find it on the ASABE Technical Library HERE (full link: https://elibrary.asabe.org/abstract.asp?aid=47587&t=2&redir=&redirType=). The article is now published, and may be referenced by the ASABE publication below:
Vol. 59(6): 1597-1608 © 2016 American Society of Agricultural and Biological Engineers ISSN 2151-0032 DOI 10.13031/trans.59.11642 1597
For more general information about Palmer Amaranth (Pigweed) can be found in another 2010 publishing on the identification and control of Pigweed in Tennessee. http://trace.tennessee.edu/cgi/viewcontent.cgi?article=1101&context=utk_agexcrop