The replacement oil tank arrived and after trying it in a few different locations, it was placed in its final position.   

The outlet is almost in the same place as teh original, so I think it will work.  Capacity is 1.5 quarts, which should be more than enough for teh sort of miles I plan on riding at any one time.

The new tank left a small wedge of space, which is far too small for a stock battery and is really too small even for a small sealed unit. 

 But it seemed to me that with a small change to that rear fender, maybe one could be squeezed in.

I had a choice of plastic or steel rear fender, fronts to choose from so I decided to use teh lighter plastic one.  First task was to cut into teh fender with a hacksaw.  Then I trimmed out a small amount of material at each side, so I could push back the flap and create a ledge. After trimming that up so teh ledge would be at the correct angle, a small amount of matreial was trimmed form teh rear of teh fender and transplanted as a floor for teh battery to sit on. 

The plastic welding isn't very pretty, but it looks like it might do the job.

Of course, without the OEM battery box, there is nowhere to hang the electrical sub panel, so I'll need to work pout where to stash the regulator and rectifier  .  Maybe a smaller electronic unit might be easier to place discretely.

The next job was to fabricate a mounting bracket for the oil tank. I started with a stock battery mount/tool tray and reduced it to a pile of bits and threw 90% away. the only part I kept was the front mount.  To that I added a 6inch strip of thin steel from the local hardware store.  A few holes and bends later and it was taking shape.  

That was one of the simpler tasks, once I finally worked out a feasible design.