I have been using 4 inch flexible aluminum dryer duct on mine, used the ends of the metal wire in the duct to ground on each end and it seems to work fine.
I got it at Lowe's and they carry it in 8 ft and 20 ft lengths.
Mike
All Gave Some,
Some Gave All.
My computer configuration and software used:
Gigabyte GA-990XA-UD3 Motherboard, AMD FX 6-core Processor Black Edition, 32 Gig DDR 3 Ram, Gigabyte HD 6450 Video Card with 1 Gig DDR 3 ram, Windows 10
Designer 2.007, Designer 3.102, Pattern Editor, Centerline, Conforming Vectors, 2d Tools, 3d Tools, DXF Importer, STL Importer and Rotary Jig.