Sorry buggy for not answering sooner... I tried posting this comment like a week ago, but lost the message and got all PO and didn't write back.
Grouped Items
Yeah... I wrote about that topic, and I'll go into a little more detail about what I mean.
-- If you have a grouped object of world type, the VIS compiler will split it up like any other world type wall / object.
-- If you have a grouped object of entity type, the VIS compiler will NOT split it up, but it will render that object as 1 whole piece. Meaning... If you hare in a large 10-floor stairwell and you're at the very bottom, and you made your rails one solid entity object, you will render the entire rail object whenever it is visible.
If it was a world type, the VIS would hide certain parts you cannot see... but because it's one large entity, you see it all.
... In short... it's easy to move the object as a whole, and since it's an entity you THINK it won't split your map up further because it touches other world objects. This is all true... but you'll see the whole thing.
You CAN make every piece of the railling individual entity objects... but you can only have ~300 individual entity OBJECTS on the map (both grouped / ungrouped).
In this case, it is best to make your rails all world type and lift the base from the ground 1-unit up instead.
As for your map and keeping the W_Poly count low for users and the CHOKE on the server lower... you can do the following:
-- Make cliffs on your map and divide it into larger outside rooms. Use the sky texture to reach from the top sky plane to the top of your cliffs to box it all off. This will reduce unneeded w_poly counts like if you made really high cliffs.
-- Make your outside cliff and ground texture higher size ratio, like 2x or 3x larger than original size. Gives you larger texture blocks to keep w_poly count lower.
-- If you have boxes and stuff, first TRY to lift them off the ground 1-unit and keep them world type. If you must... make the entities, but keep this in mind:
world objects have no "extra" hidden parameters, so they don't send much data over the server.
entity objects have many hidden parameters, and for each individual entity you have... multiply that number by how many parapeter they have AND add your texture count for those faces.
...Yeah... I don't think I need to tell you how large that number can be.
That is why my early noob_32fighter & noob_playground maps have so much CHOKE and lag / crash the server, because most of those objects on the map are entities...