Can't seem to change height of tabsheet at design or run time. Why?
Because Height and Width in that case tell you the client height and width as your visual playground.
A PageControl is the owner, TabSheets are the children, each child fit into the PageControl, so when you want a TabSheet smaller or bigger, make the PageControl smaller or bigger.
All the TabSheet heights are stuck at 791 and width at 291.
Do resize the PageControl and recheck values.
I hope this gives you a small hint.