Took a lot of elbow grease, but I was able to get the stump out without a grinder. I put a few pieces of scrap plywood against the wall to protect the windows, just in case. Here are the bits I was able to split it into 3 pieces, and it was rotten enough that the roots were soft, so I was able to dig, cut, and leverage the pieces out. Tomorrow I'll dig the extraneous bits out, as well as the extra dirt, and start filling it with the 5/8" crushed rock.