Hi Dirk, thanks - I can repeat that problem over here now.

I'll see if I can do something to fix that up in Boolean Union.

But when you have individual surfaces touching edge-to-edge like this, I would recommend using Join instead of Boolean Union. The booleans are more intended to be used when pieces cut into each other, they do a lot of extra work doing things like determining intersections between surfaces and stuff like that.

Join on the other hand is tuned up for this particular kind of case where surfaces are already touching and nothing needs to be sliced up.

- Michael