Chuck the fender extenda....
Who needs a 'fender extenda', us old trials boys use old inner tubes. Cut a length (long enough for a donkeys dobbler) and simply ease it onto the mudguard (K-Y gel may help) and hey presto flappy crappy crap deflector...try saying that after 9 or 10 lemonades...
My Honda VFR800i provided the front mudguard for a certain 'extenda fender' manufacturer to use as a mould for their production of same. I received loads of plastic stick on add ons for my part. Unfortunately the extenda fenda thingy created a fault in the mudguard; tiny cracks in the sides and Mr honda said it was down to increased air pressure ....bloody hell did I ride the old girl that fast...so I tend to steer clear of these type of mods.
But I doubt that there will be any problems with German plastic!