Progress continues on the remantling of the R90S. 
The holiday period allowed for some time in the garage and with the aid of a heater it was a decent place to work. The main thrust of this assault was sorting out the remainder of the electrical gremlins affecting the tail light. A continuity test revealed that there were problems somewhere between the handlebar switch and the tail light !! A slow process of testing every 6 inches or so located the problem in the seat pan area. An examination of the removed section of wiring revealed brittle and cracked shielding as if exposed to heat. 
Other adjacent wiring was fine, and so I replaced the wiring, shrink-wrapped the connections and put some flex shielding around the whole section for good measure.
The shocks were remounted on the bike. They seem to be fairly responsive and just needed some cleanup along with the hardware. I also decided between the 2 used fuel tanks. One had decent paint but a few dings, while the other had faded paint and few imperfections. I decided on better paint, and then used my patented dent removal system on two dents on the top of the tank. 
The patented system involves a selection of c-clamps and welding vise grips, an assortment of rags and cloths, various custom designed pieces of wood and plastic, and a few yoga moves. One dent is now perfectly repaired. The other is much improved and now looks like a minor dent. Lastly, I transferred the petcocks and gas cap to the chosen tank, and got it mounted on the bike.