Monster,
Yeah the CRD has a hole in the airbox north facing (forward) about 50mm & that plumbs via that consantina bit to a moulded bit behind the RHS head light. Not up above like the 3.7L, not sure why its like that, there is room to do something similar as yours to the CRD. Anyway I think there are 2 options. 1. Blank off that hole & bust a new one east (out the guard) to line up with the outside pipe work. or 2. use original hole with elbow to make the hole futher forwards on the guard but then the washer bottle is in the way.
Another option I suppose is to blow away the whole airbox idea & fit a purpose built airfilter housing that is streamlined enough to fit a second battery. NOw thats what Im talking about.
Having a look at a TJ, they just use flexi from the airbox all the way down to the drivers door lower hinge (near) then up & out she goes.