The bypass almost finishes KrazyDad Super-Tough v.5, b.10, #5, whether or not you start with the 4-fill and two 3-fills. Here’s my 4-fill version.

Line marking is minimal, and coloring on the few candidates remaining wraps green in r6.

With the current Basic process, we found the KrazyDad Super-Toughs much easier, compared to the  KrazyDad Insanes.

I’m incorporating 4-fills into the Systematic Sudoku Basic. They can be quickly bypassed as they arise if none of the missing values see two unfilled cells, and no missing value sees three. The disadvantage of adding 4-fills is having yet another rule to follow, and possibly overlook, in laying out a reproduceable path for newcomers, and for Sysudoku vets seeking to compare solutions.

Next I embark on possibly be my last collection review. You gotta’ stop sometime. It will be on the corresponding left pages of Heine’s Sudoku ultrahardcore 1. We’ll start with UHC 1 and follow the same skip by 44 pattern for 12 left pages.  

Your bad if you didn’t order the Sefan Heine’s Sudoku ultrahardcore 1 book for the right page review. Here’s the first left page puzzle, UHC 1.

I’m doing the left page review because of Stefan’s warning about the intractability of his right page puzzles. Maybe you’d like one before deciding if you want to tackle Heine ultrahardcores. I’ll be leaning on, and sometimes bypassing, my same two widely available solvers, and seeking, among other things, a better approach to avoiding the sheer drudgery of exhaustive ALS analysis.