Ok - took it all part and put back the thermal RAM pads .. what a pr*t ... anyway also took the time to take some more temprature readings.
New TempsThis is an update of a previous post - you're now looking at column G.
In summary, the new clamping method seems to to have actually knocked a few degress off the temps.
(ambient was 22 Deg C this time, so I corrected the temps based on this).
For the CPU, the most noticeable drop was on the base of the h/s where it was 4 degrees lower - better contact with the die perhaps ?
For the GPU this is a little unfair as I have also modified the GPU heatsink vs the stock one. Minus 3 deg C (5.5 deg F) over the die and an amazing Minus 7 degress (12.6 deg F) on the left most side of the heatsink (!).
I would put maybe 3 or 4 degrees down to the new clamping method but the rest must be down to the modding of the GPU heatsink fins (aka hack...

). So a more turbulent air path DOES provide better cooling as prooved here ...
RAM went down 1 deg C this likely because I used a different type of heatsink on the front RAM compared to my other xbox360 - I didn't bother checking all the other places as I hadn't changed them at all.
So, in summary - bolt clamping provides an equally, if not better method to get heat off the dies, and hopefully a much longer lasting solution than the X clamps !
Richard.