Most do-it-yourself books state that a sink must be done in the following way: a sanitary tee in the wall behind the sink with the vent attaching to the top inlet and the trap arm to the branch. The question is whether it can be done similar to a toilet situation, with the trap under the sink as usual, then dropping the drain through the floor to the crawl space and attaching the vent to the drain under the floor (making sure to be within the 3 and 1/2 foot limitation for trap to vent distance)? This is to avoid putting a 2" vent pipe through 2x4 structural studs (with seismic anchor) in the exterior wall. Both vent and drain will be 2" and kitchen sink has garbage disposal and dishwasher. Any forseeable problems with this configuration?