Great set up cant wait for my upgrade!
Still wanting the tea cup ray? Also tea cup ray is just the name of the size... usually they are retic rays. Can thrive in your tank however im unsure how much floor space your tank decor takes, and honestly i woudnt change it...it looks awesome!
Also im unsure about flagtails as they are known to chew on the rays slime...so i dont see why they wont chew on your bichirs.
Good Luck!