In novel writing, I hereby declare that the first rule of intelligent tinkering is:
O, that way madness lies.
I have to ask myself WHY DO I DO IT?
Once I've completed the novel (she says, optimistically) the first three chapters will surely change anyway.
Tinkering totally inhibits any forward progress with the rest of the story and saps me of inspiration and enthusiasm.
SO - NO MORE.
(but there must be a better word than 'flaming' I could use on line 1, page 4? Let me just consult Mr. Roget and his oversized Thesaurus...)