This depends on how the weight is distributed and what the cost/benefits of this extra weight are and what makes up this weight.
That's true...what part of that performance improvement is down to the loss of fat and what part of the performance improvemnt is down to whatever they did to accomplish this fat loss?
Don't worry about looking stupid...I do that all the time without even trying.
What you need though is an all over weighted body suit though rather than a vest. In a vest you'll be walking around all day getting used to the alteration in your centre of gravity and we are only talking about a minor alteration but I know you a worried about looking for 1/2 inches in performance improvement...this wouldn't be a good thing. I think it would effect you worse as an athlete more than it would an everyday Joe as you mastery of you body is what is key to your performance improvements....you could look into some detachable heavy hands made from lead that you could jetison/throw behind you just as you left the take off board...guarentee you that you'd improve you jump performance.
See...I can be constructive.