Well, I lost a stone (14lbs) in exactly 2 months, but I'm at the beginning end of losing weight, so it's probably easier at this end! It's still coming off though and I'm planning on another 21lbs by mid-may and it's looking achievable! I also remember back when I was at school / uni and my starting weight was much lower than it is now, I could easily shift a stone by eating clean & exercising every day (alone! If I went with a friend it ended up being a gossiping session not a workout!). 2 hours of swimming or ice skating most days (I love both of them so no great hardship) and generally walking everywhere, drinking water etc... I could totally do it. I couldn't keep it off though! So while you're losing, get your head straight for how you'll do maintenance, be prepared!
Oh and, don't be disappointed if you don't quite make it, because changing things up now can only work in your favour, but weight can fluctuate for so many reasons! You can definitely get a good run at it though, so good luck! Hope to see you back with a pic either way