I think you will be alright with a baffled grommet. Either that, or you could tack a baffle in there when it's raw and have it painted or powdercoated later, or better yet have a vendor do it for you.
There is adequate room between the last rocker and the rear of the cover. Same goes for top of rocker arm to top of valve cover. You'll have room to do a grommet, and probably a shallow baffle but I don't know for sure