I really like the sound of Matlida Isabelle, you get your Belle in and it is old fashioned and goes well with and is'nt shadowed by your other daughters name.
Matilda Henrietta
Matilda Angelina
Matilda Camille
Matilda Arielle
Matilda Arienne
Matilda Adrianna
Matilda Siobhan
Matilda Alexandria
Just a few thoughts..