Help with E6750 OC on a P35 DS3P rev2.1

Hi I've been searching the posts for help with this and an article on the E6750 is now not available.

System:

Motherboard: Gigabyte P35 DS3P rev 2.1 BIOS F12
CPU: Intel E6750
CPU cooler: Thermaltake V1
RAM: G.Skill 4GB 2x2GB DDR2 F2-8500CL5-2GBTD 1.8v 5-5-5-15
Graphics: Gigabyte 8800GTS 512Mb

When pushing my FSB over 400Mhz x8 (ie. 411x8) the RAM timings change from 5-5-5-15 to 5-6-6-16 and I start getting errors with orthos or blue screen, I have also run memtest and have been getting errors here too.

The ram is set to auto/normal in BIOS and im setting the RAM to run 1:1 with the FSB so RAM is underclocked from 1066MHz to 800MHz.

The system is fully stable at 400x8 and have run all orthos tests for an hour and blend test for 4 hours and memtest for 2 passes with no errors.

I increased the DRAM, FSB and MCH voltages to +.2v as advised by G.Skill and my system was stable at 410 x 8 running orthos blend test.

When I got to FSB 420 x 8 it would either BSOD or I would get errors in orthos saying rounding .5 expecting .4 or something like that (I can give exact errors if needed) temps at 420 x 8 are maxing at around 52C-54C.

I've disabled the loadline calibration, speed step, usb legacy etc in the BIOS as well and still getting errors.

Is this a case of to small an increase and I need to push it higher i.e. 450 x 8 or are their other settings that could be changed that would help (how high can I up the RAM voltage.)

I know the motherboard and the CPU and FSB can go higher than 400MHz so any help would be great.

I've already updates the bios to f12 and I tried the higher vcore voltage of 1.42 and made the fsb +.3 what settings have you used for the fsb and mch.