On a different bike I made some fender flaps out of the black plastic from Folgers coffee can lids. Quiet flexible, but stiff enough so the wind does not deform it.
I think I have bought three different sets of clip on fenders to try with that bike, for one reason or another all did not work out. Around home I use some Bontrager fenders that are 65mm wide, bought them almost a decade ago, but I do not want to do any surgery on them. I considered buying some SKS P65 fenders and doing some surgery on them like you suggest for travel, but it already takes so much time to pack up the bike, remove all three bottle cages, remove both crank arms, remove both racks, remove stem, loosen the interrupter brake levers on the bars so I can twist them, pull fork out of the frame, etc., that I really do not want anything that takes too much time to attach or remove. On my last tour, I decided to not even attach a dyno powered headlamp to the bike, instead just carried a USB powered one in the handlebar bag in case I encountered any tunnels or wanted to go to a pub at night. Used a pair of battery powered taillights, the brackets for those lights stay on the rack when the rack gets removed from the bike. The dynohub was only used for charging batteries, not lighting.
I bought some cheap small fenders on Ebay, shipped from Asia (shipping is a month) and I made my own brackets from some aluminum bar, used that on my last tour, they worked pretty well so I think I will be expanding on that concept. You can see in the photo a small shorty fender on the front wheel, have a slightly larger one also on the back wheel that is hidden in the photo. I bought a second pair, I plan to put a small shorty on the front wheel in front of the fork to keep the spray down lower, also put one between the seatstay and chainstay to reduce the spray off the back wheel onto my legs and feet.
I am usually pretty quick to put rain pants and shoe covers on when it is cold. Yes, that is a patch of snow in the photo. And sometimes when it is pretty cold and dry, I might put on the rain pants just to cut the wind.
It is a ***** to get everything all packed away in the case. It is a heavy bike, with the case it is over 50 pounds so the pedals, saddle and a few other things go in my other luggage. Rear rack also goes in the other luggage as it will not fit in the S&S case with the bike.
But it can be worth it to get the bike and other stuff down to manageable size for lugging through airports, etc. My non-coupled bikes have never seen an airport, I do not want the hassle of a full size bike box when I fly.
