B2 visa timeframe in US for a visit

[course_help_us]

Hi,
I am coming to US for a specific course which is only going to take me about 3 weeks to complete. I have received a 10 year visa, but while I am here I would like to stay about 4-5 months touring and also giving exams for NBED (dentistry) while I am here. On the visa application I have only mentioned the 3 week course that I plan to take. Is there a way I can request a 3 or 6 month stay at the port of entry? I have an aunt (mother's sister) and I will be staying with her during that time.

[peace999]

to first time tourists (B2) they usually give 6 months anyway.
to first time business( B1) visitors usually they give 3 months anyway.

For duration you can say 3 weeks course plus a few weeks for sightseeing.
That can get you 3 months easily or even 6 months depending on the officer.
I would not recommend ASKING for 6 months because that is too long.