Manfrotto 501PLONG slide plate, which balances the scope nicely on the video head (I mounted the scope at the front end of the plate, then slid it forward as far as it could go on the video head before locking down).
The only issue I have w/ the setup, which pans and tilts smoothly, is that 3 hands are needed to operate the setup: one for the scope (focusing/zooming), one for the tripod videohead handle, and one for the camera. I could pan and tilt w/ the camera / digidapter attached to the scope, but it puts undo stress on the scope/camera setup. And it would require loosening the tension on the videohead, which results in the scope tilting forward w/o the camera attached.
My other option is to mount the scope on the Jobu Jr. Gimbal Head, which allows panning/tilting smoothly and effortlessly, but then requires repositioning the scope w/ and w/o the camera to balance it. With the camera/adapter attached, the scope is back-heavy, even with the scope moved forward as far as it could go. I attempted to stabilize the rig with a bungee cord attached to the front of the scope that would prevent it from tilting back completely, but I found it ungainly. And, without a handle, it is awkward to scope birds.
The solution? Find a remote to trigger the camera.
Several options are possible. A wireless remote can be used to trigger the shutter, and costs only a few dollars, but work best when directed toward the 'front' of the camera. From what I could find, however, is that they only allow a single shutter to be captured at a time. This means no continuous shooting at 12 fps.
Sony has a neat little remote App, which can be downloaded from the Sony website. With the Sony a6300 my iPhone 7 can be used to operate the camera remotely. Its actually pretty cool; I can view the scene through the scope from the iPhone monitor, can adjust exposure compensation, f-stop, and with a touch of the screen, can focus and take an image that is now automatically saved to the iPhone. However, I'm once again forced to a single, autofocus capture and can't shoot continuously.
I would ultimately return to using the scope on the 501HDV Video Head, which is more stable for scoping. To overcome the need for 3 hands, I purchased the Sony RM-SPR1 Remote Commander.
The Sony RM-SPR1 Remote Commander is a wired shutter cable that plugs into the charging port of the a6300. When plugged in the remote allows me to trigger the shutter off-camera, and allows me to shoot continuously! With the shutter half-depressed, I can even focus. If I hold the RM-SPR1 with my right finger and thumb I can use the rest of the hand to pan/tilt the video head while operating focus/zoom on the scope w/ my left hand. With the camera / Digidapter™ attached to the scope the entire rig is stable.
Below are some shots from this morning using the rig.
The Sony RM-SPR1 is a winner.