Have you tried using the placement-map under the appearance column while designing your xlsform as outlined in the image below (it should solve your issue):

Reference xlsform:
placement-map.xls (30.5 KB)
Have you tried using the placement-map under the appearance column while designing your xlsform as outlined in the image below (it should solve your issue):

Reference xlsform:
placement-map.xls (30.5 KB)