[jeff5may]

Just grab some free ground loop design software from the web and have at it. I know that climate master and water furnace both had free stuff available a few years ago. The ones that you have to pay for are more extensive and robust, but for a single family home size system, you don't need the extra abilities.

With 4 parallel loops, you shouldn't have any head pressure woes. The more important factor to consider is velocity. The fluid has to be travelling a certain speed to get turbulence and the resulting high heat transfer. This will take some head pressure to obtain. Above another certain flow rate, the gain in heat transfer tapers off. So you want to balance the total flow between loops so that they are all in the "high gain" window. With all loops returned to the flow center, this is not difficult to achieve if you have the right size of circulation pump.