I thunk there are several people using the stock pump exactly as you described but at some point you will probably get tired of the fill time anf want to upgrade. You could add another pump to your existing thru hull intake by just adding a tee and not drilling another hole in the bottom. Or add another sprinkler valve to the end of you manifold to control the IBS. With 1100s and an IBS I would start saving up for a winter upgrade to dedicated pumps.