In a patient with gastric adenocarcinoma with +peritoneal cytology status post an R1 resection, would you consider post operative chemoradiation?

Probably not. I generally don't see a role for adjuvant CRT in the setting of positive cytology, as locoregional recurrence is not likely to be the primary issue going forward. Of course every situation is individual, and one wonders how this patient ended up undergoing resection in the first place ...

Current research is on the role of HIPEC after D2.

ESMO has some good guidelines to read, HIPEC is further down this page:

https://www.esmo.org/Guidelines/Gastrointestinal-Cancers/Gastric-Cancer

Or you can ask Dr Brian Loggie (google him, he is the pioneer of HIPEC) for his opinion.