I think it would be good if the option for show "No answer" in the "presentation and navigation" tab would also count for numerical input and multiple numerical input questions. Because this is an issues when these (multiple) numerical input questions are set as mandatory and the respondent don't want to insert a numerical answer (when "No answer" is activated, he or she can only type in an phantasy answer to continue).
Another issue would be if only some questions should have the option for "No answer": It is impossible to set an option for "No answer" for selected (multiple) numerical input questions.