Purvisll55,
I have not heard of anyone using the Rivco part you describe. Not sure I'd want to do the drilling it requires either. Have you considered HD 2-Point Docking Hardware Kit - For Sissy Bar, Solo Luggage Rack or Solo Tour-Pak? HD Part # 54030-09. Here's the description:
"Add a passenger backrest or solo rack to your Touring model. The simple choice if all you need is a passenger backrest or a solo rack, this kit contains the docking hardware necessary to install the basic Detachable accessory options on Road King®, Road Glide®, Street Glide® or Electra Glide® Standard models. Provides docking points to allow installation of Detachable Sissy Bar, Solo Luggage Rack, or Solo Tour-Pak® Rack. Does not fit with 2-Up Luggage Racks or 2-Up Tour-Pak® Rack.
Fits '09-later FLHR, FLHRC, FLHT, FLHX, FLTR and FLTRX models. For use with Detachable Sissy Bars, Solo Luggage Rack, and Solo Tour-Pak® Rack. Does not fit with 2-Up Luggage Racks or 2-Up Tour-Pak® Rack. "
MSRP US $109.95 No drilling and easy install.

I have one in new condition off my 09 SERG if it works for you. If interested, send me a PM.
GK