I was the same. I use to ride stock back in 2008 then changed to mod in 2010. I use to ride the same places on both bikes, and in my head I couldn't do it, because I was on a different bike. But once I got use to the bike, felt more confident on it, and with myself. I just got on with it!
only advice I can give is get use to the bike, might take a while. But once you know how to handle it, it will become second nature!
I went from riding a "long" bike (onza Ice) to a "short" bike (monty 221) its 20mm! Buts it rides to different! I'm just getting use to it! after 3 months!
Also think you CAN do it! rather that "oh but what if....."
Just keep at it fella!