I pretty sure the Crud Racers will fit with at least 25mm; I've got a set left for my Silvio that I should really test out.
Crud Racers works on front wheel with 25 mm tire without any problem, only two more holes are needed to fix it to chainstay bridge in the front. But on the rear it does not work out of box, I had to turn stays inside out to clear rim and still it is pointing little bit to one side as one stay is mounted on tube and another on on disk brake calliper mount.
For 28 mm tire I think that booth mudguards will need some tweeking (I have ordered 28 mm Pro One). On the front wheel It will need some fixation on the back side of the fork cown. At front of crown mudguard is fixed to brake bolt, there is enought clearance, but on the back it will need more space. On the back wheel I am not sure that there is enought space to clear brake bridges, I will test it.
I think that there are a lot of V riders who don't need to ride century under 4 hours but ride in every weather so mudguards are need.
EDIT: I will do some photos of my Crud Racers as home work for tribe.