[MattyMatty]

When does a map cause lag?
When the objects are too close? If so how close is too close for objects,when they are combined?

Does the san andreas map count as objects,
(example)would it cause lag if I put half of a skyscraper in the road in lets say Ganton?

How much objects can I put in an area without it causing lag?
For example I want to put objects in Ganton,how much objects can I put there?

[Schneider]

I think it totally depends on the processing-power and connection-speed of your host. The more objects that have to be streamed in, the more calculations are needed by both the server and the client. As long as the server can keep up with it, it shouldn't cause lag.