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Have you tried using a barlow with the dob for your photos? Surprisingly, the stock standard 1.25" 2X barlow GSO makes is pretty good.
Not knowing what dob you have (if I've read it, sorry I can't remember what it is), it most likely will have more aperture than this Vixen refractor, and the resulting f/ratio in the dob will be a little faster. If you have a barlow (2" if you have one), you will get a handle on what it is like to deal with a long focal length without expense. You are used to the workings of your dob, so the learning curve will be shorter too.
I hate to say this, but that tripod you have will not be able to deal with that Vixen scope, and forget the camera. A ball head is not made to take such and extended/long item, and the moments of inertia will overwhelm it. As Steffen said, you will need to overtighten it all the time, which will shorten its life, and will only be a source of frustration. "Isostatic" systems are what you need. These are ready made, like the Vixen tripod Steffen linked to, or you can make an isostatic jig for a standard photo tripod like I made for an 80mm refractor - see pics below. When the tube is balanced in alt, I leave the clamps open when I'm using the rig, and the scope stays put. The second lot of pics shows the same sort of isostatic jig I made for an AZ3 mount with an 100mm refractor. The pics show if nothing else, how an isostatic situation works - like the Vixen Porta mount, the altitude pivot point is in line with the centre of gravity of the scope loaded with stuff. This way there is no excessive force being placed on the altitude bearing as it is a balance situation. Though I still think that an f/11.4 80mm refractor is too much for a photo tripod.
I have a 2" 2X ED GSO barlow you can borrow for the exercise. I don't use it much - haven't in over a year.
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