@timbukktoo , in general, I would agree that you could reach your goal of avoiding interest and penalty charges by this process -- the whole thing depends on the exact figures. Suggest a careful reading of section 6654 of the IRC -- there are a lot of ands ifs and buts. The easiest way to stay clear of the charges ( addition to taxes under chapter 1, 2 and 2A would be to pay all dues by Jan 15th of 2021 or pay all dues and file a return by Jan 31st. of 2021. I am attaching a link to the section of the code -- takes a little patience to read through ( you can skip over all the non-applicable parts ) -->
--> https://www.law.cornell.edu/uscode/text/26/6654
