Good day from DownUnder:-)

I am designing new mudguard for new utes and but I have come across to one edge that needs to have a smooth transition from 90 deg down to 45 deg.

( see photos bellow ) and MY PART SW ATTACHED.

I have done it using Surface Loft Feature ( pretty dodgy :but I need to get this done different way so it will also be a part of Flat Pattern.

At this stage, the mudguard looks ok but its only cosmetic. The Flat-Pattern is all wrong.

I am not sure how I could possibly do it. Can you help guys? Thank you so much :-)