Definition UI resource would be in the form: "pihcoremoduleid:htmlforms/checkin.xml" where "pihcoremoduleid" is the module nameartifact id as specified in the pom.xml, and the form lives in the directory "omod/src/main/webapp/resources/htmlsforms"
NOTE: that it will *only* pick up new updates when opening a form in "ENTER" mode--it will attempt to load the form from the file system and then save any changes to the form definition in the DB. Loading in "EDIT" mode will load the form from the database, *without* checking the file system first. This works for both entry of new data and editing of existing forms
Special thanks to Unknown User (mogoodrich) for the tip