I was reading the manual, and it says the maximum bit diameter is 30mm. Any tried anything wider? Were there any problems? I would like to use a 1/2" round over bit, but the diameter is 38mm.
When you say 1/2" round over I assume you mean the cutting edge radius as the shaft diameter for the OF1010 is either 8 mm or 1/4".
My OF 1010 is not with me at the moment but you need to check if the large diameter will fit in the base opening otherwise you will not be able to set the height right. If it is a 1/2" cutter edge radius then you would certainly need to cut in more than one pass and so it is essential that the cutter will fit up into the base opening.
I've just checked mine. The casting aperture is about 52mm, but the plastic dust shroud (which is removable) reduces this to about 48mm.
Perhaps the guidance to use smaller cutters than will fit the base is because the bearings in the OF1010 are small and would struggle with a large out of balance cutter, but I really don't know. Just make sure you don't run a cutter that size at too high a speed; I'd recommend using speed setting 1.
I've run bits around 40mm before no problem (1 5/8"), though they were bearing guided bits, and so the the router was only running 1/2 that diameter through the material at any given point. No problems experienced.