Basically, something like this...

Each person gets their own dialogue box. The portraits of the characters are 150x150 pixels, so dialogue boxes need to have a 150 margin I would assume. Height 150, Length 400. Also think I would like that to be the maximum and minimum size, so the box is always the same size.
I've been running into issues though, so here I am! Thanks in advance for any help.
(I don't know if it's possible to make dialogue creep in from right to left instead for the people on the right, but that would be neat if possible.)