Good luck. But if expect BTC to rise 20% in that time, you are better off using a different exchange.
Why should I? I've bought on BitStamp at 810 USD, sold on MtGox for 960. Then I'm some 30 USD in plus. I have to subtract two trading fees (cost of learning...), SEPA fee, which will be around 2 USD, then my bank will automatically convert EUR to PLN at some not very interesting rate... Still should be worth it. How is bitcoin priced in 6 weeks is completely irrelevant, it may be even 10 USD... Well, if it will be 1500 USD, holding would be better 
. The worst what can happen is MtGox total collapse and my money lost.Of course doing arbitrage with 0.2 BTC is pathetitc, but I want a proof of concept for myself.
My thinking is a huge whale has already tried unsuccessfully. I'd say in the beginning of January was a good time. But we're almost at the end of Jan 31 and other then China and FBI's BTC is the only predicted bad news on the horizon. So there's a higher chance now that BTC will go up 20+% in those 6 weeks in which you may not get your withdrawal.