OK, my RS400 arrived today, along with the SR7010, and I've been able to confirm that both units are working, and to start testing things out, specifically with reference to the cable.
I purchased this PlugLug 25' Cable
for $9.99 (!) and initial testing is positive.
I'm using an ordinary Sony BluRay player for initial testing, connected to the JVC with an Amazon Prime Cable. I configured the SR7010 to put out "4K (60/50)", 4:4:4. It took the JVC a little time to do the switch, but then it carried on without apparent problem.
When I checked the Info/Settings to show what the JVC was detecting, it showed:
Source 4K (3840) 60
Deep Color 8 Bit
Color Space YUV
I didn't see any setting on the SR7010 to increase color depth to 10 bit, so I'm not sure I'm fully testing the 18Gbps capacity of the cable.
Basically, I'm wanting to have the SR7010 output simulate what it would be doing if I had an actual UHD BD player attached to it, to make sure this 25' cable will pass the signal properly.
Is the test I've already done adequate to conclude that this PlugLug cable is up to the task of doing 18Gbps, or do I need to change settings somewhere to accomplish that?
P.S. Please excuse the taped up sheet acting as a screen, plus the washed out image! I want to test things out to make a final decision on screen size, and the blackout shades for the various doors and windows haven't been purchased yet! One thing at a time!