The problem with just lowering the laser speed is that the powder is still not hot enough to stop the warping and in fact just lowering the laser speed actually makes the warping worse as there will be a bigger temperature differential between the sintered powder and the non-sintered powder. I have tried a lot of things to stop the warping and my solution is that there is no substitute for powder temperature - get that right and the warping disappears. The next biggest problem is trying to make sure there is even temperature all over the build area. I think this is more difficult to achieve.

You are right, the parts are more difficult to clean but at least they are good parts. You could try lowering the powder temperature to 173.7c. I do most of my printing at this temperature and the parts are easier to clean but I cannot print within about 30mm of the edges. It is near the edges that we have the biggest problem of uneven temperatures. I am thinking of devising some kind of reflectors to try and get the temperature more even. I'll let you know how I get on.