Sidis will stretch out to fit your foot. If the Megas are a touch loose now, they'll be really loose 5k miles down the road. I have a fairly wide foot and bought G4 Megas (also in a 45) a few years back that I ended up replacing with the standard G4 Carbons. The only time I ever wear the Megas now is when it's so cold that I need both a shoe cover and a think pair of smartwool socks.