If Glock would just give in and make a carbine people wouldnt have to come up with such strange things. That said I saw a video displaying this from shot show and thought it was so neat with all the nice features like covering up your ugly Glock.
I have Roni-g1 conversion with full accesories ( accutact angrl sight , micro T1 sight , shell collector ...etc ) for my glock 19. I do strongly recommend it . Even I tested with glock 17 with full auto function .. U just need to take care of the pins ! And be aware of the fake cheap one ( build for Airsoft ) !!!!