If I understand correctly you are concerned that the bottom menu will open down and not be seen. I am currently working on a icon menu near the bottom and was concerned with the same issue. I believe the drop "down" is controlled in the styles.css by a "top" attribute.
So it seems to me there are a couple of choices. Create a new id for your menu and create a new style in a custom css file and link the files... Or add a new style to your page... or add an inline style.
to do an inline style - this seems to work in a quick test I did:
go to the specific in question and replace with this: <ul style="top:-20%;">. (yes a negative number)
This will override the top attribute set up in style.css. Play with the number of -20% until you find a suitable number for your menu.
There is also a "bottom" attribute that would probably work instead but I found that this worked- at least in a quick test.
As I develop my "bottom icon menu" further I will be playing with the numbers. Right now I have my icon menu set high enough on the page that its not an issue and my submenu opens down but I will be dropping the entire icon menu down and will eventually need to open "up-wards."
I'm sure support will give us the correct method for opening "upwards" but for right now you can try my solution and see if it works.
my icon menu is at www.achieva.us... it will eventually open up- just not yet.