I have ordered an P6/K6 > E-mount adapter to use my medium format 6x6 lenses, 2,8/80mm and 5,6/250mm lenses on my A7 and A6000!The lenses are quite heavy, and comparable bulky, but having also an advantage! I am using the center of These medium format lenses only, so to speak the sweet spots!
Optical may be not as crisp as 35mm glasses, but with high contrast, no distortions, no corner vignettings!
On my A6000, the 80mm lens is an 120mm lens with an close distance of 60cm. Not too bad für an 120mm focal length!