How to split Windows Terminal with 2×3 equal sized pane on startup?

I want Windows Terminal to startup with 2×3 pane that are equal sized, but with the command below they are not equal size:

"startupActions": "sp -p "Bash" ;  mf left; sp -p "Bash" -H ; mf right ; sp -p "Bash" -H ; mf up; sp -p "Bash" -V ; mf down;  sp -p "Bash" -V "

I can do 3 vertical next to each other with the same size but I can’t move to the first pane for the horizontal pane:

"startupActions": "sp -s .7 ; sp ; mf left ; mf left"

TDLR: I want this: https://i.imgur.com/iNh2byx.png

But I have this: https://i.imgur.com/R2bMLT3.png