My gap was also very little. That was the reason when someone was leaning on the countertop the grout cracked between the wall and the tiles. I used the color matched caulk instead of grout between the countertop and the tiles. And it works pretty good. No problems so far and no cracks. We live in Ohio and we have hot summer and cold winter and the expansion - if any - did not result in any cracks of the caulk. you can see in the pictures that the tiles almost sits on the countertop...I hope that I do not have problems later because as you mentioned to go back it is almost impossible.