My little setup with those half loop siphons work fine with small pea gravel in the cups,
and it drains the entire system dry automatically when siphon mode kicks in. I am wondering
with your beds having a greater amount of media in them than what I have in those cups
will your grow beds drain the same way with out stopping and more than likely there
should be no reason they won't.

By the way I think flex hose method is great, we have not had any troubles using hose
siphon, we used that in all setups all summer 2008 in more than one system and they all
worked.