I agree that D-72 did not produce the greatest results with Polycontrast Rapid. D-73 is a contact paper developer, quite similar to my favorite, Defender 54-D. 54-D did produce notably better results on this paper, but maybe not as good as desired. Note, however, that Polycontrast Rapid changed often and considerably over the life of that product name. The last versions were really pretty good.

Kodak D-73 cold tone developer for contact papers
Water (52C) 500 ml
Metol 2.8 g
Sodium sulfite 40 g
Hydroquinone 10.8 g
Sodium carbonate 75 g
Potassium bromide 800 mg
WTM 1 l
Dilute 1:2 for use. Develop 45 seconds at 21 C.