I like my Dixon Trad D whistle so much that I’m contemplating the purchase of one of their ABS whistle/piccolo duos. As a possible alternative to waiting for a duo set to cross the pond, I found a vendor in the States who has a Trad D piccolo with a brass body. Does anyone know if the piccolo head would fit on the whistle body, and vice versa?
Just tried it for you. 
Yes, the tube is the same one on the Trad brass whistle & piccolo. 
The duo are nice instruments too, I have both ‘D’ & ‘C’ models - play well as either whistle or piccolo.
Many thanks! Be it a brass Trad or an ABS duo, I see a piccolo in my future.
Edit: there is indeed a brass Trad D piccolo in my future! I’m excited about it, and cautiously optimistic that I’ll have a duo set sometime, as well.