Hi Alex, boolean union in MoI can sometimes get confused with a large set of objects like that if it happens to try and union together 2 non-intersecting pieces to start with.

So in a case like yours you can get the boolean finished in MoI if you do it in smaller steps.

You'd need to start out with 2 crossing pieces like this:



Then by progressively moving down along that diagonal adding 2 more crossing pieces at a time I was able to successfully boolean everything in MoI.

MoI automatically sorts objects that are processed in boolean union so that the largest and smallest pieces are combined together, so that helps to avoid this "order of processing" problem for cases with a large base object being unioned with smaller pieces sticking out of it but it doesn't help in your kind of situation here.

I have it on my list to investigate exactly why Solids++ is sensitive to the processing order for boolean union and it's probably solvable but I expect it to be a time consuming investigation and so it won't happen in the v4 time frame.

- Michael