Hmmm maybe I think theres smth called the jdec table or smth that comes with most new laptop memory telling the memory how to behave at certain speeds, I've never seen a 7 as part of a timing set, lowest I've seen are 6s. The only way to tighten up timings I found was to buy 5-5-5-15 ram at 800mhz, and its jdec table stated it ran at 4-4-4-12 at 667, which is how it works in my laptop now. That and you can use programs like setmem or rightmark memory analyzer to adjust your timings, you can adjust EVERYTHING with them, EXCEPT for the CL (first number) timing....which blows being that its fairly important.
If you had a different chipset (not intel) that mod would've worked!! I'm remembering it for future reference
The easiest way for you to overclock is to get a t7600g and to flash your laptop with the m1710 A07 bios. That way you'd get core 2 duo support and be able to have access to all multipliers. If you're interested, the t7600g has a cpuid of SL9U5, and there's many programs out there that let you force flash the m1710 bios (and to extract it from the dell installer program for it).
An m1710 is IDENTICAL to the e1705. The only thing missing are soldered connections for the led lights and sometimes the dock. I'm fairly confident a flash to an m1710 overclockable bios is safe.