You can either drill another 100', which is almost boring, or you can get creative. Lets say you don't have much room, and you must get 200' ft of pipe in the ground before it goes down your borehole, and another 200' after it comes up again out of the hole, (400 ft total to get you the missing 1/2 ton capacity you need) you can built a 4' diameter slinky with 1.25" pipe with a 24" pitch. So you run a 25ft trench out to the well, overshoot by 5ft, run the pipe back to the well, and the return pipe coming back from the well you run in a second trench back to the house in the same way, right next to the first one. That way you could get 400ft of pipe into the ground in (2) 25ft trenches. Just a thought. Yes, you can run it in 1" pipe for 30ft (incl. hose) for supply and return, and then convert over to 1.25" pipe. Just confirm your heatloss and that it will be 2 ton unit.