The problem, as you know but didn't explicitly state, is that taking an extra retirement withdrawal will also (eventually) increase the taxable portion of social security. I would try the TaxCaster -- don't add the solar credit -- and fiddle around until you get to $6450. There should be a details page where you can see the details of the calculation and not just the final number, but Turbotax had kind of hidden it, because they want to use the TaxCaster as a tool get get you to use the program.
The IRS also has a tax calculator that can do the same thing.
https://www.irs.gov/individuals/tax-withholding-estimator
One note of caution: The Turbotax TaxCaster uses 2024 tax rate tables and deductions, so the math will be off slightly. It should slightly underestimate the amount you can withdraw before paying tax. So I would double-check sometime in December, using Turbotax for 2025 (either online or installed on your own computer) to see if you can take a little more.
