Most people do run oneway diffs now Rog, the only people I can think of that dont are Yardy & Daz! It might be worth taking a look at Yardys D4 setup.
From past experiance when ive gone from a good setup with a oneway diff to the same setup with a diff in the front its understeer city
If I was you id try Rich's setup to the letter, it allways looks good