Killer Sudoku solving strategies

Someone wrote to me that puzzle 126 of the new "Colossal Killer Sudoku" book was especially difficult.

I started solving it, and got a start in it pretty quickly. I'll describe the steps below, and am inviting other

puzzlers to add suggestions

Here's the puzzle:

Some initial steps:

- the sum of all cages in columns a, b, c, and d = 184, so e4 = 4

- the sum of all cages in rows 1, 2, and 3 = 146, so a4 + h4 = 11: doesn't help me much,

other than determine that a4 cannot be 1

- using similar steps, d6 + f6 = 12 (doesn't help me yet)

- the "17" cage at d8d9 must hold 8 and 9

- so the "11" cage at e7e8 must hold 5 and 6

- so the "17" cage at e1e2e3 must hold 1, 7, and 9

- so e5e6 must have 3 and 8, so f5 = 1

- so e9 = 2 and f9 = 3

After these steps (more or less):