Thanks for the replies - I see this isnt' an area most of us have any experience in. I might have to try the dedicated wet plate photographer's pages to see what they do for location work.
"To gain advice on the benefits against "other" materials, you first must tell us what material that "pop-up collapsible/portable darkroom tent" is made of..."
There is no description of the material used in the only model I've been looking at which is too small:
https://www.theimagingwarehouse.com/ProductGrp/Nova-Darkroom-Tent
"If you want low cost diy, the hydroponic stores sell blackout plastic sheeting. The white/black material isn't 100% lightproof everywhere but the white/black/white sheeting is."
Thanks John - this is the silver mylar hydrophonic material which I've been looking at to use as a second layer over a 3x3 metre gazebo frame. It's for recurrent use - so the set up time and the potential for leaks or cracks in the material which needs to be folded for storage when not in use is important.
"Ventilation and temperature - especially if multiple people are in it! If it's very hot, or very cold out, it becomes more critical. Also, if you use blackout cloth, make sure it's for photo purposes. Regular blackout curtains, don't block all the light - so you need some mutli-layered set up, (i've used blackout curtain and black foam core.) You can buy a popup frame, - the type used at outdoor, flea and art fairs."
Thanks - these issues aren't problematic being indoor and using positive pressure active ventilation. I guess there aren't any many ready made gazebo sized darkroom tents readily available on the market.
Kind regards,
RJ