Check the drawing here of my 130w panel. Distance "E" to the "ground"
I used this panel (not grounded) with my LandStar controller(if grounded needs a positive ground) and my neg grounded (to frame of RV) battery bank, with no problems.
http://files.sharpusa.com/Downloads/Solar/Products/sol_dow_ND130UJF.pdfScroll down to page 10 here for the drawing. See how they have the battery positive grounded. I did not attempt to ground the panel nor the controller and the battery was neg grounded. Everything worked.
http://blog.digit-parts.com/pdf/ls10242024.pdf