The default account is a micro lot account. But you can simulate any account size as described in the manual under "data import".

The margin is NOT increased as the account grows. You must increase it manually and very carefully - increasing the margin too fast is the number 1 reason of margin calls with automated strategies.

By the way, it can be mathematically proven that setting the margin to a fixed percentage of the account balance will ALWAYS cause a margin call sooner or later - no matter how small that percentage is. This practice is one of the many reasons why private traders normally lose all their money. The margin must grow slower than the account. When your account has doubled, increase the margin only by a factor 1.4, not by a factor 2.

A MT4 plugin is planned for January 2013.