I tried this one summer a long time ago with a 14' flat bottomed day sailor. Worked great until the lines tangled and eventually chafed through. It is rather distressing to come down to your mooring field and see neither boat nor float.
The boat drifted ashore across the harbor about a mile or 2 away and someone pulled it up on shore.
We retrieved it and it was basically fine but this would not have been the case if it was a keel boat.
New mushrooms should cost about $1/# and less for a used one.
Here is a thread about a boat that was left on a single anchor:
http://www.sailnet.com/forums/genera...ly-sucked.html
I second Sailingfool's advice.