On my hard tail emtb.. I came across a mudguard set in tkmax. It needed cable ties and silicone to fit them but they did a better job than what you have. On my full sus emtb I used mudhuggers which were expensive but didn't stop the back spray. I think you will have to accept that mountain bikes throw crap up your back.Any recommendations??
I have then on my road bike and are brilliant but no good for wide knobly tyres