It always helps me to get a new guy as soon as possible, seeing the tank stand empty is just too depressing for me =/ Some doubletail bettas have really prominent caudal peduncles (it's the little oval shaped bump that every betta has on their bodies, just before the caudal fin starts). It's not anything to worry about, it's just the way their bodies are built =) Flaring is great sign of health, an active fish is usually a healthy fish! I'm so sorry about Claude, he was a pretty little guy =( I hope things go well for you with your two new boys!!!
My Current bettas:
Sullivan- Orange rose tail halfmoon male
Daisy- Mustard Gas (black and yellow) veil tail female
Milton- Teal butterfly halfmoon male (mom's betta)
DFTBA to nerdfighters working to decrease world suck!