How to constrain read area in Lunchbox ExcelRead in Human UI

I have an .xlsx with 4 worksheets. All sheets are laid out the same with particular columns & the same number of rows to pull data from. I know how to constrain the Excel Reader Legacy, but that one requires that the .xlsx be open. The new one doesn’t need that and is happy with the path component in Human UI. When I select the different worksheets, I get very different amounts of data one sheet to the next. It varies from 398 lines of flattened data to 721 lines. The domains I need change from worksheet to worksheet.

Any thoughts?

TIA Robb