Alexis Powell
Natural history enthusiast
...when I get a new pod and head...
One of the nice things about Manfrotto/Bogen is that they have replacement parts for everything (in my experience, even for most discontinued models). If you otherwise like your tripod, you should be able to get a new complete center column assembly, to which you can attach a new head if the old one can't be fixed. I don't follow your description of the slotted center screw, so maybe the following isn't relevant, but if you are trying to take off the top plate and head together for some reason, the top plate on the center column of many models attaches via a hex nut that is reached with a very long socket extension through the length of the center column. If that doesn't work, you could saw off the top inch of so of the center column and go from there. Also, keep in mind that you may be able to get replacement parts for your broken head. I just had the cast metal part that clamps the handle on my 700RC2 head fail (it cracked in half on a cold day when I tried to quickly fold my scope downward for carrying). The replacement part is $6 direct from Bogen/Manfrotto. Wish this bit were made with cold forging or machining (I ordered an extra replacement for future use).
--AP