Without a proper tension method it can be tough. A 1/2in is a long ways.

You can make a magic gear work but an eccentric hub is better. It has enough adjustment in it that I can run a 16t fixed and 18t freewheel. Personally, I am glad I went this route. The wheel is now in its second frame (cyclocross) and if i ever go to a frame with horizontal dropouts i just need new axle caps. They make them in standard and eccentric in every width you could want.