Ok,
So now we are really talking about my sphere of influence
The reason you can make 180 and not 360 is simple!
The action to make 180 is a standard ski technique; you just ski up the hill, but quicker. You probably think of it as a “Hockey Stop” only done slightly more actively ...
The reason you will stop there is because you are leaning very slightly forward and possibly looking at your skis
You MUST stand upright.
As you get to about the 160 mark, stand bolt upright and keep your ankles, knees and hips fully extended. Now use the leading hand and shoulder to “look” for the remainder of the turn.
As for the skis, you must be able to sense a non-edging ski and allow it to be absolutely flat. Any edge will reduce your rotation and stop you half way. (As you have found)
Once you have got this sorted you will discover that you can edge very aggressively into the first 2/3rds of the rotation but then you must totally release the edge and allow the skis to be completely flat.
I once read a post by Pavel who said that skis are very shy and if you look at them they get silly and behave in a random way. This is very true for spinning. Look UP, look ROUND and NEVER look at your skis!
Perhaps tomorrow I will post some video of the various stages of spinning
What ever you manage or don’t, make sure you do it with hope in your heart and Elan in your soul!
I am happy to answer questions like this all night long
Jan