I would say that your only other tang options are going to come from the zebrasoma family with that size tank. I would not put two Ctenochaetus tangs in together. You will get others to say that you shouldn't add any other tangs to a 4' tank, but if you are going to do it, I would stay with one of the smaller zebrasomas (yellow, purple, etc)
On another note, I have personally found tomini to be aggressive, so a new tang may not do well if added after it. I had a tomini kill a goldflake angel once.
I would just stick with one. If you want another, I agree a smaller (not sailfin) one from the Zebrasoma *genus* would be the best choice. The only way I've had success with yellow in a 4' tank is when it's the only tang. They eventually got mature enough to kill other tangs or even butterflies.
I have a scopas tang that's about 2 inches long and planning on a tomini down the line. I love the coloring on the scopas he just swims around and picks algae off rocks all day. My favorite of the 4 fish I have.
The scopas is the best bet, I have one and all the ones I've known have been pretty tame. Pics dont do them justice if you havent seen one in person. Mine doesnt utilize a huge amount of real estate, I like their perfect spade shape and personality.