Yes I am sure the branded adapters from Fuji and others have better material and precision mounting.
With el-cheapo adapters...your mileage may varies with each one...some have poor fit even within the same brand, lens may wobble slightly etc...
I used the el cheapo China adaptor from HK...
http://ebay.to/18nFZME
Got the Fuji X-A1 for around SGD$300 from Japan. Quite a bargain for an excellent APS-C sensor.
You can check out some of the night shots taken with Rokinon 16mm/F2, similar to Samyang...
https://flic.kr/s/aHskaLZS7f
and this
Lake Te Anau by kok hong, on Flickr
These photos are truly amazing and inspiring. Takes a lot of effort planning the trip/equipment/location...and a bit of luck :-) to get the aurora display/timing.
Thanks for sharing.
Here's some shots taken during a recent trip to South Island
Fujifilm X-A1 with Rokinon 16mm/F2
Lake Pukaki Cottage night sky by kok hong, on Flickr
Dawn @Lake Pukaki by kok hong, on Flickr
Dawn@Lake Pukaki by kok hong, on Flickr
Flkr Album
https://flic.kr/s/aHskaLZS7f
Some photos taken during recent NZ trip
https://flic.kr/s/aHskaLZS7f
Dawn@Lake Pukaki by kok hong, on Flickr
Lake Pukaki Cottage night sky by kok hong, on Flickr
Its one of those cheap adapter from Ebay (hong kong vendor).
http://ebay.to/18nFZME
Yes I couldn't get the same sharpness on M4/3 (G3/G6/GM1). So perhaps it is really the adapters that makes a difference. Don't give up on your CV35/1.2.