As Alan said -no mushroom is gonna prevent all damage in every type of crash. You're just looking to minimise it
However those ones at teh start of this thread are utterly pointless -look at the mounting point, its the fairing stay FFS. That piddly bit of alloy would buckle if you leant on it, let alone dropped 200kg of VTR onto it!!!!
Other things to bear in mind
The R&G ones and those M&P ones require cutting/ drilling of the fairing
I've got the rhencullen ones and have been impressed with them -the main selling point was the bracket they mount to is sturdy -to my mind the DHM/ Motrax ones are a bit flimsy looking
The other problem with those DHM/Motrax ones was they mount further back and I kept clouting my knees on them
However, my mate crashed his Storm at Mallory. Went down on the left side, flipped over onto the right and the Motrax ones he had on meant my track fairing he was borrowing (never again!

) didn't have a mark on it!!
Look back through earlier threads and there's some pics of them