That's the nature of any web-based survey.  Until there are more formal studies done on FOV, all we have to go by are personal accounts and occasionally articles like the one published by Dr. Sebag recently.

Just a suggestion, but perhaps the survey can be moved to web-based like Survey Monkey or something.  I think the free account limits it to 10 questions and 100 responses, but I think there'll be less than 100 respondents here.