With at least a few tweaks, I think the Dot Studio is one of the best values out there. Worst thing that can happen is For a Casino -- assuming you now have a stop-bar tailpiece -- a Vibramate V is clearly one option.
Here is a picture of the model: Make sure that wire is in direct contact with the metal surface of the Bigsby -- you will probably have to remove a felt pad in that spot -- and then reinstall it over the mounting screw so that it sits between the wood surface and the ground wire. This one has the Xtrem FT mounted, which I like just fine.
They come in 2 sizes, so check the ordering instructions to make sure you get the right one.
What you like, what sounds good to you, and sometimes maybe even what's available in the moment did Epiphone perhaps have B70's sitting in a warehouse? The Casino does not have a stop bar tail piece.
The top vibrates differently on the two designs, with the hollowbody top being allowed to vibrate and resonate more freely than the semi hollow, which is attached to the rigid center block.
As far as break angle, I would venture to say that a person's playing style would be a big factor in having strings come off of the bridge.
Keep in mind -- you will need to run a new ground wire to the Bigsby. In response to your question about a B30 on a hollowbody, yes, Epiphone has had success with it on the Swingster, pictured at left. If the ground wire is between the wood top and the felt pad, you tailpiece and strings will not be grounded.
There are certainly a lot of opinions as to whether that's 'correct' or not, but correct is probably not important. I'm leaning toward just going for it. If you decide to install a B7 by itself -- you should be fine with mounting screws drilled through the top without a center block.
Add a Bigsby to Epiphone Casino?
That's the basis for my previous statement of not wanting a unit with a tension bar, which requires being screwed down to the top, on a Casino. Note- there is very little break angle over the bridge on the Swingster.
Run a new ground wire from that additional hole -- solder one end to the ground wire from the pickup; wrap the other end around the mounting screw for the Bigsby. The other question is a matter of you like the looks of it.
In the center is the semi hollow Epiphone Dot Studio with a B70 that's been added by me.
Gather all the info you can, get what you think will work best for you, and casino applications play your Casino for all it's worth. Personally, I don't have any issues with it, but have seen it happen to other players.
I'm of the opinion that a large chunk of metal that you screw down to the top of a hollowbodied instrument is going to have a large impact on how that instrument sounds. It seems like many people just go ahead and drill through these tops with no center block.
Remove the bridge pickup -- you will see a ground wire attached to it that ground connects to one of the threaded shafts for the stop-bar stud bolt. A hollowbody guitar is a much different animal than a semi hollow.
An aggressive style may well benefit from a tension bar. It will add a couple of ounces to the guitar's weight oz.?