Weightloss bet

robisonfire

So in an effort to get these last twenty or so lbs off I decided to make a bet with a friend. I'm 5'11 215ish and have a fair amount of muscle definition. He's 5'9ish and i'm guessing 275+. I need help to figure out a way to make this bet fair for both of us because Its going to be a LOT more difficult for me to lose more weight than him in the 60 day period we agreed upon. I googled it but I wasn't very successful. I thought about doing a BMI vs BMI against him but he would still have a considerable advantage since he's just starting to work out after gaining a lot of weight and i've been slowly losing for like 2 years now. I'm open to any suggestions anyone can offer. Thanks.