I've tried both Flexi-Flares and just the rubber strips from Clark Rubber.
Imho, if looks matter then go with the Flexi Flares.
I tried to save a bit by going with Clark Rubber on the rear,
but for the effort I put in, installing at least a dozen screws
I didn't like how the edge of the flare looked warped at some spots, since there's no tension.
I now have extra Clark Rubber 35mm fender flares
in approx 1.5m lengths (2) and another strip about 50-70cm long
which would be perfect if anyone needs to throw some on to make their Subaru street legal.
Any takers?

Flexi-Flares:
-come with self-tapping sheetmetal screws that work, but are a big pain;
go buy some quality self tapping screws with bigger screw heads (more pressure) and can cut the hole easier
-lubricate the hole where the trim rim goes with lots of lube. I used Lanolin...
else your fingers will get sore very quickly trying to force it through dry rubber,
by the time you're about 40 cm in; too far in to pull out

I made my Flexi-Flares run the entire length of the wheel-well and mud-flap.
With the trim ring to add tension, I have a smooth arch over all tyres that nearly looks factory-installed.
