One possible solution you could consider is having two variations of the survey (not necessarily a second survey, though) ~ ask the participant if they'd like to take the short variation or the longer variation. Listing the number of questions each variation has would also be a good idea.
Granted, I'm not sure what the standards are you need to abide by, but if it allows for that it'd be something to consider.
One possible solution you could consider is having two variations of the survey (not necessarily a second survey, though) ~ ask the participant if they'd like to take the short variation or the longer variation. Listing the number of questions each variation has would also be a good idea.
Granted, I'm not sure what the standards are you need to abide by, but if it allows for that it'd be something to consider.