I am now trying to figure the easiest way to mount one of my camera/lens combinations to allow me to take some pictures.
Purchasing the TC definitely was a very good choice! It makes things easier and more reliable - and faster.
Waht do you mean "the easiest way to mount one of my camera/lens combinations to allow me to take some pictures."?
Do you mean how to find the NPP for your lens(es)?
The easiest way is to detach a battery-grip - if you have one attached - and to use the short part of the rail to fix the camera in portrait-mode. That is what you should try first.
Depending on the lens you use this rail might be a bit short - there are longer ones.
So i suggest to figure our which lens you will use as your main-lens and which lens(es) you will use additionally.
When i got my Merlin 5 years ago i detached the L-bracket first and used only the short rail with the screw to take my Canon 20D with a Nikon 20mm lens.
That worked from the very start. When i switched to a 5D2 i had the rail nagged away 2mm in thickness to meet the NPP (the 5D2 is built a bit higher than the 20D) - no big deal.
Now the flattened part is in the mount and the camera is fixed on the thicker end. Matches perfectly.
Hope this might help a bit.