A quick look at registration records shows just one Gastrochilus retrocallus hybrid, Gastronopsis Nanzhi Pink (Phal Wedding Promenade x Gchls retrocallus). Wedding Promenade is typical first generation miniature breeding with Phal equestris, so your proposed cross with Kenneth Schubert is a new direction in Gastronopsis breeding. There are only a few other Gastronopsis hybrids from other Gastrochilus species.

Good luck with your new plant and the cross. Interesting choice. I would take a flask of that hybrid if I could get it.