The solution to consistency for putting seems to be a cylindrical putter lopakagolf.com
Wouldn't changes in that putters elevation off the ground change the effective (negative) loft .......something that a flat face doesn't do. It'd be an interesting thing to goof around with.. I believe Yoda had a negative loft putter once upon a time , not sure if it was flat faced or not or what his conclusions were.
A few things to consider in all of this: Homer was a pool player and his putting mat was a well worn , nearly bald carpet remnant.
BTW Homer's opinion was that consistent putting came with a consistent Hinge Action (any of them but there were implications of course) . He believed that once a Hinge Action was mastered you didn't really need to practice putting as much . That one day wonders and inconsistency gave way to the easy fine tuning of path and Hinge Action.
Im still waiting for that day to arrive personally ....