Any known issues with overlapping objects?

Is there any known issues with overlapping any of the following three in any combination?

1) Solids

2) Displacements

3) Props (Static)

All experienced mappers know it is bad to overlap solids in any case, my question is in regards to overlapping any of the above listed.

EXAMPLE:

Solids + Solids = problems

Solids + Displacements = ???

Solids + Props = ???

Displacements + Displacements = ???

Displacements + Props = ???

Props + Props = ???

Uh...I don't know, but personally I'd stay away from having the same types of objects overlap each other. I'm guessing the others would be relatively ok (though overlapping in general is a no no).

there is no big problem other than some performance issues with overlaping solids

displacemnts dont block VIS and are very cheap, overlapping them seems
to work fine for me. you can always turn on mat_wireframe 1, 2, 3
and check if there is brush break up.

as for props, if your talking about static props then I dont see any
problem, you can put them half way through walls, or each other.
only problem might be with shadows but you can always work with those
on a model by model bases.

<DIV class=quote>
<DIV class=quotetitle>? quoting DrGlass</DIV>
<DIV class=quotetext>there is no big problem other than some performance issues with overlaping solids

displacemnts dont block VIS and are very cheap, overlapping them seems to work fine for me. you can always turn on mat_wireframe 1, 2, 3 and check if there is brush break up.

as for props, if your talking about static props then I dont see any problem, you can put them half way through walls, or each other. only problem might be with shadows but you can always work with those on a model by model bases.
</DIV></DIV>

Just a note to those new to mapping:
DrGlass is right about the overlapping of solids but keep in mind that it is never a good idea to allow this to happen in your map. Your compile time can take a major hit if you allow solids to share the same space (non-entity brush objects). Other problems (severe in some cases) will arise also, depending on the complexity of the solids overlapping.