I found this on a wiki:

The optimum mixture and conditions for reversing yellowing of plastics:

1) Hydrogen peroxide solution, the stronger the better. 12% works fine; 6% works also, just more slowly.

2) Approximately 1/4 teaspoonful (4.9 ml) per gallon (3.8 l) (1/3072) of Tetraacetylethylenediamine (TAED)-based laundry booster (concentrations of TAED vary).

3) UV light, either from sunlight or a UV lamp.

I also read the TAED wiki.  I suspect that is where Oxy Clean comes in.

I might try the above. Thanks for all the advice.

jack