A couple of thoughts. I would try whole wheat, rather than rye. I would start with 4 OZ of flour and 8 OZ of water. It's important to be fairly precise in the beginning. If you don;t have a scale use 1 cup of flour and one cup of water. This is a 200% hydration, really loose. The feeding should be only once a day for the first few days. You need to give it 24 hours to fully digest the meal.
As to the quantities you feed, it has to be at least 100% of the starter you're feeding. If you start with 12 OZ (4 flour , 8 water) you need to feed 4 flour and 8 water. THis gives you 24 OZ, so at the next feeding it should be 16 flour 32 water. You will intitially be dealing with huge quantities. But after 3-4 days you can begin tossing half of your concoction and feeding the remaining half.
Peter Reinhart's starter from Crust & Crumb uses raisin water in the beginning. Soak 1 cup of raisins in 2 cups of water for 15 minutes. Toss the raisins and measure 1 cup of the remaining water to use in your day 1 starter. The sugars from the raisins help jump start the process.
His complete starter formula and commentary can be found here:FormulaCommentary