yes, i believe it is illegal.

I would play a 3-0-3N-1-3 and hope for a goal-fest up the middle.

-------ST---ST---ST-------
-----------AMC------------
------MC---MC---MC-------
---------------------------
-------DC--DC---DC-------


If you are worried about his DML/DMR coming up the flanks, go with:

----------ST---ST----------
------------AMC------------
--ML-----MC---MC-----MR--
----------------------------
-------DC--DC---DC-------

Up the middle of course.

He can park the bus, but if you play offensive and cover your butt, the 80/20 possession from the illegal formation, coupled with the offense, it should be a win for you.