Thanks to this question, I've managed to get Terminator to open at a particular size, with the right configuration of child windows.
However, they don't open at the size/position that they were in when I saved the layout.
Edited To Add: The layout portion of my config file contains lines like below. The first part ([[[child0]]]) is the main window, while [[[child1]]] is one of its children (as indicated by the parent = child0 line). Changing the number in the line that reads position = 1237 has no effect that I can see.
[[MyLayout]]
[[[child0]]]
position = 27:29
type = Window
order = 0
parent = ""
size = 1052, 1853
[[[child1]]]
position = 1237
type = VPaned
order = 0
parent = child0
I've tried adjusting the position = NNN lines in the childN sections, but to no avail.
(As a bonus question, if they aren't there to set the size of those windows, what are those position lines supposed to do, anyway?)