A 5 wrap would get you right around .80 with 5mm legs. Going down to .50 I think you should use 26g wire as long as the Uno will handle wire that thick. 28g will be difficult to get a .50ohm coil as it would have to be very small. This would not be good for flavor or vapor production.
edit:
If you dont mind taking some pics I am interested in the Uno and I would like to see yours set up![]()
I'm expecting it in the next couple of days. I'll take a few pics and post them. Thank you for your help.