Job well done! I have contemplated how I will move my RTC in 10 years, when he is full grown, and I move across the country. Sedation is a great idea, and the improvised sling was ingenious, as well. I will have to experiment with the dosage as well, starting very low, considering the catfish skin.
Don't know if this has been answered or not yet (didn't feeling like reading however many pages this was), but what's going in the 2,500? A giant pacific Octopus would be pretty sweet. Although I guess it probably wouldn't work out so well if the two tanks shared the same water/filter.