Common sites for Cushing ulcers include all of the following except -
Cushing ulcers are stress ulcers that are associated with intracranial injury or an increase in intracranial pressure.
About the site of involvement in Cushing ulcer, the maximum information I could get was from Robbin's. It states "Gastric, duodenal and esophageal ulcers arising in patients with intracranial injury, operation or tumors are desig­nated Cushing ulcer"
So the best option to rule out is distal duodenum, as almost all duodenal ulcers are located in the proximal part.
Also, Know
Cushing's ulcers are more prone to perforate than other stress ulcers.
Esophagus
Stomach
1st part of duodenum
Distal duodenum