Hi Roof
We have a Skywatcher 200 x 1000mm f5 Newtonian Reflector which was originally fitted with a rack & pinion focuser, the same as your scope.
In order to reach focus with our Pentax ist DL, (which is similar to your K100D ) we purchased a Lumicon Low Profile 2" Adaptor.
This adaptor when fitted on to your T-Ring will allow your camera to fit close in to your focuser giving you the extra in travel to achieve focus.
The only problem is that in order to use this adapter you will need to make a spacer as the inside diameter of your focuser is larger than the diameter of the adaptor.
I made a spacer using plastic water pipe with a 52mm inside diameter.
If you want to persue this avenue I can make a spacer for you - gratis off course.
The Low Profile Adapter can be purchased from My Astro Shop per this link
http:www.myastroshop.com.au/products/details.asp?id=MAS-266
Page one of our web page, listed below shows some of the images taken with this set up.
Hope this helps
David