Nine years ago, prompted by a similar thread I experimented with a DIY front fender flap. I ended up with a yoga mat secured to the fender by three nylon bolts. I thought I'd have to replace the mat every couple of years but here it is nine years of all-season snow and rain commuting and it is still intact. A couple of years ago I added a thinner black flap to the outside (a dollar store floormat) mostly for cosmetics, but also to keep the flap from flapping at speed.
When I bought my new main commuting bike in 2015 I also bought SKS longboards in the longest size and mounted them to the rear of the fork crown to rotate them further down in the back...no additional flap was needed.
My other fendered bike is my 2007 Dahon Boardwalk folder. Its front fender needs to be longer, but reduces road spray enough to keep my feet relatively dry, but not as well as the other two bikes. At some point I will probably see how lengthening it affects its foldability.
