555.
No bumps on the forehead. the exhaust fan hood is actually about to get them from the stove exhaust hood would 4" or 10mm in from the outer edge of the counter top. I've done plenty of stove top cooking and not once hit my head on the exhaust fan hood. to do so, I'h almost have to make a conscious effort to do so. I actually went to the stove and stood in front of it and really would have found it difficult to hit my forehead on the exhaust, unless that is I wanted to get my face in the frying pan and then, and only then would have had to make a conscious effort to avoid the exhaust fan hood. otherwise, no worries. appreciate your concern though.
one thing I would have done differently though is to have lowered the shelving above the counter tops. the counter tops are 35" or about 90mm from the floor and the bottom of the shelves are abot 26" or 66mm above the counter top. that makes it a little high for the average Thai woman. We manage though so no worries.