visitor visa - to and fro, canada

[ssrpk]

I am currently in USA on a multiple b1/b2 visa, and my I-94 is valid till march 16th. I will be doing volunteer research work at john hopkins, baltimore, which will be probably till june or july 2008. Due to lots of problems associated with extension, is it safer to go to canada and stay there for a couple of weeks before re-entering United states, to make sure that i can have an exit stamp on my passport....or shall i apply for extension?

which one is safer? what kind of problems can be faced upon re-entering usa from canada?

any experience?
thanks

[Murali]

the Canada route is not guaranteed, and you may not get I94 extend that way , since US immigration authorities are aware of such short cuts and often don't allow I94.
Best way to apply for extension.

[ssrpk]

thanks a lot, i have the same perception