I find I'm prepping several of these this year as well, as the withholding advice I gave people in the last year hasn't happened because they don't quite know how to execute.  We attach an envelope for the local office.  

It's not a difficult form to complete, but I'd just as soon have it within the Lacerte file rather than creating it on irs.gov.  

I'm finding that with inflation adjustments to tax rate brackets that those pensions that use the usual W-4P have had withholding decrease even as the benefit increases.  Being able to cover the shortfall with withholding calculated by percentage is a good solution.