I have an 09 Evo. With the exception of the front bolt I took my fender bolts out and just use wire ties to hold the fender on. This gives the fender a little more flex and helps to prevents cracking. If do bail hard enough to break a wire tie, I simply replace with another tie. I keep about a dozen wire ties, wire tied to my bikes rear brake hose so replacing them is easy. I replace the front bolt with one thats a little longer and use a rubber washer. This helps a bit with the flexibility of the plastics.
As for the vents in the fender. I used aluminum tape, applied to the underneath on the rear vents to keep water out. Theres still plenty of airflow from the fronts. The screen is held in place with glue from a hot glue gun. I had to repair that once last year.