try it on a test DB -- you'll be suprised: it's one of the gatesware features that works well.
the A-database splitter does a reasonable job but will take the wrong guess if (eg) you have a tblThisUserConfig which should be local to each user. whatever - it's easy to "unsplit" such a table with a delete & import at the frontend followed by a delete at the backend.
my view: even if you are not doing a multi-user thing -- split anyway! i often need to look at data in a bizarre one-off fashion with a query - i keep a trash frontend pointing at my backend just for this
you might also want to browse you favorite search engine / A-help / this site etc etc for stuff on optimistic/pessimistic record locking.
I have now split the database and all seems to be well. There was a couple of things I needed to move to the client as I had user details that then fed into another table for audit purposes, but yep this seems to work well.
Stay glued for the next problem,
Cheers for your help.