I used 53mm sks guards (bluemels I think) on my pompetamine. Worked real nice with 38mm paselas. Not what you're after but quite close. I would recommend going a bit wider than 45mm.
I ran 42c under 45mmm guards for a while. Obviously water spray doesn't bend around corners very much so you stay mostly dry but it did come out the sides onto the drivetrain/my feet
Anyone squeezed 40c tyres under 45mm guards? I'm not riding my pomp, mudguards will help remedy this