Baz, just some inside experience of the RC12 from GSO.
Focusor, through that away. It is ok but cannot haul a decent load up hill. Start looking at focusors with 6-9kg capacity and those that allow automated focusing (you will want to use this later so think ahead now). Some starting points are Moonlite focusors, Feather Touch focusors and FLI Atlas. Each are progressively more expensive, but each are strong. Look at rack and pinion on the Feather Touch. I am not sure if Moonlite make a rack and pinion but take a look there too. Each focusor has to be 3" to protect the light path from the mirrors. You should not use a 2" on these scopes.
For OAG go with the MMOAG from Astrodon. Best OAG in the business and built like a tank. If you can get hold of an STL11000 camera then the MOAG is the going to work better than the MMOAG. If you want to use the stand alone OAG the MMOAG will work for you. It is pricey but worth the money. Good fittings and places that make adapters like Precise Parts will know exactly how to fit that together with other components.
The Loadstar is a good camera but also consider the ST-I from SBIG. It has its own shutter and that means a lot of if you plan on doing a lot of unattended imaging. Don't get me wrong the Loadstar has great credentials but just take a look around. Buy the best guide camera once. The SSAG works too but it was a temporary measure from my own experience. It served me well but in the end died and many months before that it was act up and not calibrate properly.
The scopes you have will be fine for wide field imaging on their own but I would just pick one and use that one on top of the mount. Work on the premise that you want about 3/4 weight capacity of the mount for total setup. With that you need to consider camera, focusors, OAG's and cabling. It starts to add up after a while and this will get you quickly close to the 3/4 weight capacity of the mount.
Personally if you consider that the gear you are going to buy is high end, then think of the RC12 as a temporary resident of the system, you may decide later to buy a bigger scope and or a more expensive scope altogether. Buying the expensive peripheral components means you don't have to upgrade again and that will save you money. Don't balk at the costs as reliability is precious in my opinion. Stuff breaking down late at night means lost time.
The RC12 is a good scope but you need to tame a few issues. Focusor is one and the other is dew protection of the secondary. These scopes dew up on the secondary, so consider putting in a dew strap by Kendrick. I found it works a treat and then keep the fans running all night on the primary. The metal tube is another but refocusing every half and hour keeps that under control.
Buy yourself a Tak collimation scope too. You will need it and it is a good tool investment for all future scopes. I found my RC came a little out of collimation in the primary and I needed to sort that out. The only way you can do that is by using a Tak collimation scope. You can use Ken Crawford's avi (on his site) which shows how to collimate the rear cell on a RC scope.
If you think of anything else you want to know by all means ask. I am more than happy to help with frank and correct knowledge from my own use, not some supposition posited. These scopes have good optics but you need to work a little to get them working well. Don't believe half the crap that you can read about the GSO RC scopes or the innuendo that appears on this site from certain individuals. Those people have their own agendum to get people to buy some other telescope design. Their comments constantly appear in the GSO RC threads and each time their comments deride the scope and yet I have never seen them actually say they have one or tested one or even imaged with one.
Let me know if I can help further.
