IMO using the "start line command" is not the way to follow for a scrolling menu system.

Every time you need to scroll the menu by one line do a complete screen update by removing a line and and adding another one. This can be achieved by looping over the menu array so that every time a scroll is required print eight entries by moving forward/backwards in the array. For example print entries 0-7,1-8,2-9,3-10 and so on... Also you may consider advancing eight by eight in the menu array for faster scrolling. In any case, you may also need a cursor so that the user can select a menu entry. Redrawing the selcted menu entry in negative would also be a nice touch.

If you need to create some complex hierarchical menus, a Circut Cellar article titled "Hierarchical Menus in Embedded Systems" by Aubrey Kagan may help.