I did not like the way the shoulder harness was installed on the RV10.  Since I was updating the interior to be more car like,  I decided to use inertia reel shoulder harnesses in the front and back seats.  After searching on the internet for seat belt companies, I found one named Seat Belt Pros located in Freeland, WA.  I ordered a generic seat belt assembly for mockup in the RV10.  This company is very good on working with you on what you want.  The price was about $75.00 per inertia reel seat belt assembly.
Front Seats
The front seat belt retractor was attached to the back of the front spar.  I made doubler plates to go on either side of the spar for the retractor attachment.  A 5/8" hole is then drilled through the doubler plates and spar.
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After installing the retractor with a 5/8" bolt, I installed a 1" x 1" x 1/8"thick aluminum angle over the retractor to add resistance of the retractor moving upward.  This was probably over kill.  The aluminum angle is attached under the seat track brackets.
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An aluminum cover was made to enclose the retractor front spar area.  Inverted nut plates were attached to the seat track bracket and flush screws were installed.  A slot was cut in the cover to allow the seat belt to go through.  Nylon guide blocks were attached in the cutout.  The seat belt "receptor" was located next to the center console.
Click pictures for larger image
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Back Seats
The back seat's bottom cushion is larger than the seat bottom with the kit.  The back seat belt receptors were relocated in the center of the cabin area.  A 5/16" threaded rod connects the two seat belt attachment fittings supplied in the kit.  Steel spacers were used to position the receptors in the middle of the back seat cushion.
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The inertia reel for the back seat was installed on the cabin cross bar.  A reinforcing plate was installed on the cross bar in the location of the inertia reel attachment.  A 1/4" thick aluminum angle was installed on top of the cross bar.  A nylon guide block was installed on the aluminum angle.
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A cover was made to hide the seat belt inertia reels.  The nylon guide blocks extend through the top of the cover to guide the seat belt over the top of the back seat.  The oval hole in the cover is for the headset's wires to exit.
  Front Seat Back Seat
Web Length 110" 110"
Cable Buckle 13" 4.75"
Color Tan Tan
Shoulder Mount No No
Items Ordered
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These pictures show the attachment of the retractor to the spar and the belt installation.