As long as it aint leaking gases out or air in....and you can feel the difference,then its OK
However,the preferred option is a piece of steel around a quarter inch thick and some kind of gasket....depending on the alloy it might not last that well...but then again it might,so let us know how you get on.If you havent taken the EGR out then you wont have to block up the little hose and I cant see that you need to do anything else....but Im sure someone will put me right on that......