I have the Simmonds glass ones. I find that they do reduce wind buffeting to my face. It may depend on your expectations as to their effectiveness. If you are hoping for a draught free cockpit, don't put the hood down!
I liked the inside fitting for the reasons given above but I did find that it was more difficult to get into the car with them. They only fold in far enough to lie parallel with the side screens which means they poke into your face when getting in. My +8 is pre-long door.
I modified the mounting blocks so the wind deflectors fold in against the windscreen. I had to mount them about one inch higher to clear the scuttle which required bespoke stainless steel draught excluders. A bit of a journey, certainly not "plug & play". However, they are very nice and now swivel a full 180 degrees .
