Scope will probably work at reduced aperture with this configuration, and focal length will probably be well over 2650mm depending on the exact configuration of the visual back and diagonal connection.
It is a lot of light path for a C9.25.
Now that only matters if it matters to you, and if you don't mind the aperture loss, I guess that is fine, but my advice is to use the Baader 2.6x GPC when you do planets because along with the aperture reduction, you will be adding in the range of 1/5th wave of spherical aberration to the system. For DSO you may not notice this, but for planetary use, you will have trouble outperforming a 120ED if you don't use a strong barlow or GPC.
If you are using some kind of visual back, you can save about 30mm of light path (about 100mm of focal length) by directly connecting the diagonal mirror housing to the SCT visual back and using the Baader SCT Locking Ring to set the diagonal position.
Ken Hutchinsons vignetting analysis covers the issues of aperture loss and focal length increase so if you have some questions about this post, I recommend that you find a copy and review it. C9.25 starts to loose aperture when the back focus goes much over about 180mm and your configuration is going to be in the area of 230mm (minimum, probably more if you are using any kind of visual back) so you are looking at less than 9" of aperture and a focal length increase of maybe 400mm.