Anyone know how to get Complex Collision on DM's?

I have a Mesh with my desired Collision, but when I make a DM out of that Mesh - the collision is not complex anymore and obviously different. Can anyone explain why this happens & how to fix it??

Destructive Meshes are complex (vertex based) and can’t be any other way.

One thing that causes problems with DM collision is scaling; being that you should avoid doing it at all costs. Make sure your DM’s scale is set to 1, 1, 1 - this typically means playing with importing scale if you need to make it the correct size in your level.