Congratulations on a fine job!!! That's a great set-up you have shown. I especially like the plastic bleach-bottle cones with the hanging receptacles. Were the cones nailed to the tree? How did they work for you?
You might find plucking easier if you zip-tie the legs together and hang them at shoulder level. I use a discarded porch-swing frame and wire hooks, and can use both hands at once to pluck.
I like your sink set-up too, I've been asking on Freecycle for some kind of sink, a kitchen or laundry one. Did you have a bucket under the drain? You're right about having things set up high enough to avoid back strain, about elbow height seems best.
Perhaps next time you could put a trigger nozzle on the hose, then you could keep running water handy and have it shut off conveniently in a moment.
Those sure were big testicles on that roo, how old was he anyway? I toss those and all the other organs except the intestines to the living chicken spectators that hang out around the table.
I have a processing pal, a butchering buddy who comes over every time I have birds to do. She & I are continually devising better ways to do the job next time. I'm going to show her the photos of your plastic cones, we might try making those.
Congratulations again, and do enjoy the tasty meals those birds will provide!