I think you can do this in the ini file. Under the [MenuStates] section.
These should be the vanilla numbers:
Spoiler [MenuStates]
MenuStat=1.7 0.4893 0.4297 0.5010 0.4110 0.4883 0.4492 0.0210 0.0213 0 1 0
MenuMagic=1.7 0.36 0.88 0.50 0.15 0.36 0.51 0.98 0.79 0 1 0
MenuMap=1.7 0.9795 0.8763 0.5238 0.1684 0.3652 0.3724 0.9877 0.0145 0 1 0
MenuInventory=1.7 0.9795 0.8789 0.5238 0.1505 0.4492 0.3698 0.0213 0.8781 0 1 0
MenuConsole=1.7 0.9795 0.8750 0.5238 0.1875 0.4893 0.3125 0.5105 0.0606 0 0 1
MenuInventory-MenuContents=1.7 0.98 0.88 0.50 0.11 0.45 0.37 0.02 0.88 0 1 0
MenuContents=1.7 0.9795 0.8750 0.5238 0.1875 0.3887 0.3698 0.8435 0.8781 0 0 0
MenuDialog=1.7 0.9795 0.8750 0.5238 0.1875 0.6973 0.4375 0.5161 0.9514 0 0 0
MenuInventory-MenuBarter=1.7 0.9800 0.8800 0.5000 0.1100 0.4500 0.3700 0.0200 0.8800 0 1 0
MenuSpellmaking=1.7 0.00 0.00 0.50 0.50 0.00 0.00 0.50 0.50 0 0 0
MenuBarter=1.7 0.9795 0.8789 0.5238 0.1505 0.3799 0.6289 0.9795 0.7123 0 0 0
MenuRacesix=1.7 0.0000 0.0000 0.5000 0.5000 0.0000 0.0000 0.5000 0.5000 0 0 0
MenuStatReview=1.7 0.0000 0.0000 0.5000 0.5000 0.0000 0.0000 0.5000 0.5000 0 0 0
LastMenuUpWas=-1
MenuSkills-MenuCreateClass=1.7 0.0000 0.0000 0.5000 0.5000 0.0000 0.0000 0.5000 0.5000 0 0 0
MenuSetValues=1.7 0.0000 0.0000 0.5000 0.5000 0.0000 0.0000 0.5000 0.5000 0 0 0
But you can change the size, shape and placement to anything that you like just by using the mouse in-game.
Personally, I find the vanilla menus size/shape/placement to be pretty bad, and always change them to fit my needs.
(using the Code Patch, you even have more freedom on what size/shape you can make them with the "Unrestrict menu size" option)