Dude, having an upward curve is a good thing because it hits the G spot better, therefore women like it more. If I were you I would not change what you are doing. But, if you really must, I did the search for you and it seems that the general consensus is to jelq downwards. Also, when you jelq, use and overhand grip. Some also believe that doing the inverted V stretch helps.
I must say though, that many believe fixing a curve comes a lot harder to most than gaining.
I miss this place.
Old stats: not sure but not much smaller
Currently: BPEL: 7.5 EG: 5 Goal: The holy grail of course. (8x6)