tmux/tmuxinator custom pane layout

Question

i'm trying to use tmux/tmuxinator to set up a terminal window with multiple panes. Here's what i've done so far:

1. started a tmux session
2. split my panes and sized them how i want them
3. ran tmux list-windows to get the layout
4. included the output from tmux list-windows in my startup_profile.yml file
5. ran tmuxinator start startup_profile

when i run the command in step 5 above a new terminal window starts up with the correct number of panes but the panes are not the dimensions i want, they are smaller both vertically and horizontally from what i want them to be.

i have 2 questions:

1. what do i need to add/subtract/change in my .yml file to get the panes to be the right size?
2. i'm really ocd and would like to specifically set the size of my panes, not just go off of what "looks right" when i eyeball the size of the panes. how to do i change the values in the layout: section of my yml file to adjust the size of the panes to the exact dimensions i want?

Here's what my .yml file looks like:

name: startup_profile
root: ~/

attach: false
on_project_exit: tmux -CC attach

windows:
  - dev:
      layout: 382a,80x60,0,0[80x10,0,0,0,80x10,0,11,1,80x10,0,22,2,80x8,0,33,3,80x8,0,42,4,80x9,0,51,5]
      panes:
        - pane1:
            - blah1
        - pane2:
            - blah2
        - pane3:
            - blah3
        - pane4:
            - blah4
        - pane5:
            - blah5
        - pane6: 
            - blah6