Really a good mix with perlite is required for a healthy grow. The soil should drain quickly. Yes it will raise to the surface when you heavy water very good point stinky but you can put some construction grade sand on top and then that is not a problem. Plus you will never have alga growing on your soil if you use a layer of sand on the top.

Even up to 50/50 mix is fine but you would water a lot but most use 60/40 but you should use more then 80/20 that would be a little hard and hold to much water.