If there are wire splices in that "SHALLOW CEILING PAN" it is undersized. Even if not, I would venture it is still undersized but there are models with 6 or so cubic inches volume. Replace it, splice on pigtails if you need more length. Some luminaries have integral areas you can add to your cubic volume with, provided they are listed and labeled as such.

Thanks, dudley, I have not thought about box fill before. This box seems only to be designed for covering with something that will extend the capacity. At 6 cu in, I can't do anything with it because just entering it with 14 ga and leaving it with 14 ga adds up to 8 cu in. Is that correct? Ouch! That means that there is no way to make a 6" box work in any way. I've been looking at pictures. I see a 6" pancake box that has two integral cable clamps. That does not make sense if I have the calks correct.

Are there any similarly-sized, round, but deeper box that has a cable entry at the periphery? That would be great. Even better would be an extender. This location is about 16' off the ground so a little added bulk is not going to make much visual difference.

I really need a small, but deeper box that has an entry at the back plane at the periphery (not center). I can't afford to let this thing turn into a project that takes several hours tearing apart the eaves and rebuilding them to get at the cable and reposition it. It might not even work anyway since I don't know the direction from which the cable approaches. I'd like to have a working light there, but I'll abandon it before I spend days to do carpentry, paint and install a new box. I can't afford to spend a bundle on it either.

Ditch the pancake box, install a romex connector in the 1/2" hole and wire directly to the new fixture and attach it directly to the surface.

You are, of course probably right. I just have to do some poking around to see if I can find a box that sits properly and will work with what cable I can free up from inside the structure. With any kind of luck, I can make it work without too much trouble. If it looks like it is going to turn into a huge project, I will have to just put some kind of cover on the pancake and abandon the light for now. I suppose I could go back to rebuilding the old jelly-jar light that was there. I just have higher house-fixing priorities right now. I thought this was going to be relatively easy :-(

The shallow boxes are typically used with fixtures that have a canopy which can accommodate the wirenuts. Obviously that canopy has UL listing for splices/connections since nothing isolates the canopy from the wirenuts, no matter what box is used. That canopy has a volume but it is not necessarily specified.
An LB with volume posted on it can be used for splices providing that the same volume considerations are applied as to boxes. If this works on that basis, the original box can be removed. An LB with NM connector on the short leg can be installed on the existing cable and the long end of the LB can be secured to the other (new) box with a chase nipple or an all-thread short nipple and locknuts, depending on the spacing desired. Not the prettiest thing one can imagine, but code compliant.

Thanks for the explanation, bus_driver. I followed the first part, but got lost in the jargon for the latter part. I know what an NM connector is, but what is an "LB"?

Ion, you often post answers to electrical questions. One assumes that you have far greater knowledge of the subject than the norm. Forgive me for that.
Google can be useful.

http://en.wikipedia.org/wiki/Electrical_conduit#Conduit_bodies

Thanks, I'll have to puzzle out the best combination on the trouble/cost matrix to fix this up.