hello,it can fit sigma contemporary 150 600mm.the compartment inside the backpack is removable, you can DIY according to the size needed. 

Equipped with eyepieces: H6mm, H20mm The multiples are: 300/6=50 times, 300/20=15 times. If you choose a 3 times Ballov lens, the magnification is 50X3=150 times, 15X3=45 times; plus a 1.5 times orthographic lens, the imaging is a positive image, and the magnifications are: 50X1.5=75 times, 15X1. 5=22.5 times. Namely: minimum magnification: 15 times, maximum magnification: 150 times. 

It’ll be fine for 50 feet! I’m not sure of the exact range but it works great at 50. 

Yes. I have the same lens and adaptor on my Sony a7ll and it works beautifully. The m42 is also known as the 'universal' mount as other 3rd party camera and lenses also used it. I own 6 other K&F e-mount adaptors to different lens makers (ltm, MD, CF/CD, Nikon) and they all are well built with a nice snug fit. Highly recommended. 

I actually have not received this adapter yet. It's shipping from China. Don't think that was disclosed in the ad. However, I do not believe this is for the Pentax Q body rather for digital and film cameras that take the Pentax K mount in its many variations. So I'm expecting to be able to mount my Leica M mount lenses on my digital and film Pentax K mount cameras, no autofocus or relay of exposure information, only to be used with manual focus and exposure.