Cross-examination on the Sit vs. Stand/Walk Option

This is a common fact pattern with nearly infinite variety -- assume the person needs a sit vs. stand/walk option at will, every 30 minutes, every hour, etc.  Vocational experts identify cashier, assembly, and bench work.  Some identify clerical occupations.  The key is curiosity.  

I am fascinated by how people know bits and pieces of information.  Did you read that; someone tell you that; or just have anecdotal experience with that particular phenomenon?  When vocational experts testify to the existence of work, they bring out the enigma box with the label, "I have 30 years of experience."  That is sufficient if we let that statement ride.  

How many times have you performed a job analysis on this cashier occupation?
How many different regions of the country have you been to and conducted a job analysis of this cashier occupation? 
Do you believe that you have a statistically relevant sample on which to extrapolate to the 155 million jobs in the US economy?

It is not enough to complain that the vocational expert has just made up testimony out of whole cloth.  The representative needs to ask questions that prove the lack of statistical basis for the testimony and either a concession that the Department of Labor does or that the vocational expert is ignorant of whether the Department of Labor collects that data.  Then go get and present the data to the ALJ.  

Cashiers have the option of sitting vs. standing/walking at will in 5.6% of jobs. 
Cashiers are on their feet 87.5% of the day at the 10th percentile.  

The vocational expert testified to 300,000 cashier positions requiring light exertion with standing/walking limited to six hours in a day.  The add-on of the sitting vs. standing/walking option led to the vocational expert eroding that number by half.  The ALJ will find 150,000 jobs significant; everyone in process knows that.  These two Occupational Requirements Survey reports first gutted the existence of light cashier jobs that require six hours of standing/walking and then eviscerated the concept that half of light cashier jobs have the sitting vs. standing/walking option.  

There are 3.55 million cashier jobs in the nation.  Cashiers don't require a high school education nor do they require either work experience or the acquisition of work skills per the OOH.  The ORS tells us that 20.8% of those jobs require light exertion.  How many cashiers get to sit for at least two hours per day, when they want to sit, for as long as they want to sit?  The statistics don't parse down to answer that question but our first quest is to prove that the vocational expert lacks the foundation to tell us that the number is half the cashier II jobs cited by Job Browser Pro.