The hole setup (Canon 7D in prime focus of ETX70) turned out to be questionable because of several reasons.
(1) The camera is too heavy for the telescope mount. There is no easy way to achieve any reasonable balance with any kind of counterweight that would not stress mount mechanics.
(2) Focusing is not possible without extension or Barlow lens. This adds to the general balancing issue as the it increases the lever of already badly out of balance scope+camera assembly.
(3) Finally, even with live view provided by Canon 7D it is extremely difficult to focus precisely enough due to the atmospheric turbulence. Autofocus, of course, is not an option in this setup.
As the result, the images even though have higher pixel resolution, fall short of the images obtained with a more modest setup. However, live view offered definitive advantage of Canon 20D where focusing was even more challenging.
The image in this post is a manual composition of two best images in the stack of about dozen of reasonable images. Very likley like most of the fine details of the sun surface are actually CCD noise enhanced by processing.
I contemplated this setup for imaging the eclipse 20120520 but opted for a simple and more robust one Canon7D with EF 70-200 f/4 lens with solar filter attached.