@Monkey Mja
Here,
Have a go at this, will be updating it soon again.
http://forum.thegamecreators.com/?m=forum_view&t=167375&b=21
Yes you can CSG floors however the CSG flag needs to be active on the floor mesh.In order for flipping the mesh you can do that in any free 3d editor but to do it quickly, you can use lithunwrap quick and simple.
There are problems cutting multiple meshes with a single mesh that will cause so problems.So it is recommended to cut/slice multiple mesh csg into smaller sections into 50 x 50 unit meshes that way you can use the FPSC segment editor to do each section.In the FPSC editor you can align the different sections up to create a multiple mesh CSG.
It is recommended to pre-cut floors by using FPSC segment editor as it can cause some problems cutting floors and walls in eal time.
Quote: "You don't, unless you want problems, as FPSC does not like csg in floors as it can really cause problems.
You are better of making floors (ground) pre-made with the holes you want (in my personal opinion)"
@Nbt
99% of the time the problem is the CSG, floors works no different to walls in that sense...
Just been chatting to my neighbours teenage daughter and it turns out she's big into UFOs and aliens.
Which is cool because tomorrow she's getting abducted.