Hi Chrissyo,
I have a 10" GSO dob and I have had to make major mods to allow focus for my Canon EOS 20D (same focal point as 400D).
To see my mods see this thread:
http://www.iceinspace.com.au/forum/s...ad.php?t=18909
and finished result:
http://www.iceinspace.com.au/forum/s...ad.php?t=19212
All this was needed as the mirror is too far away in standard form. Even a low profile focuser would not have been enough. I cut 35mm off the bottom of my scope and now it "only just" comes to focus with my standard crayford focuser and 20D. One way to test where the focus point of your telescope is, is to hold a piece of paper infront of the focuser (no EP) and point it at the moon. By moving the paper in and out you can see the focused image of the moon on the paper. Hold it where you think is sharp (This point is where your CCD needs to be) and measure the distance from the focuser to the paper. This measurement shows you how much room you have for your adapter and the distance from camera front to CCD.
I cut 35mm off as this is the size of EP spacer easily bought from bintel. You could cut 50mm off and use a 50mm spacer/extender. As an extra bonus your tube becomes shorter, lighter and more managable.
Hope this helps and doesn't confuse!
Dave.