Thank you, Richard, for the reminder about your tests of the reflective material. There were tons of data, and some if it didn't stick.
Coincidentally, Warmlite had similar problems when it first began laminating reflective mylar to its tents. Don't know if they fixed it, but they still sell tents with reflective material many years later, so they probably did. Richard states it is any easy fix.
Guess that is the chance we take buying or making tents using advanced materials made by small companies developing new stuff. After a lot of hemming and hawing, and the help of a lot of info on this site, especially Richard's posts, I decided it is worth the risk, as have many others making/using cuben shelters and reporting good results. But not everyone gets to be a winner, apparently not the Rocket tent people, unfortunately. Haven't seen much of the older model, but the newest model looks to be excellent for maximum protection at minimal weight.
No doubt there is something of a greenhouse effect with cuben in a tent. On another thread about the reflective cuben, someone pointed out that many of us wanting light shelter for long distance treks use the small tents in the dusk, dark or early morning, or in the rain when there is also no bright sunshine. The cuben is available tinted, which affords privacy, and looks better IMO. So not sure there is any need for the reflective material among trekkers. Maybe it is a different story for climbers - don't know.
The only real drawback of a tent with the tinted cuben in the summer might be that when arriving at a campsite in the sunshine well before dusk, you would need to wait until later before putting up the tent. On the other hand, in colder weather, putting up the tent early would allow it to gather some heat. Not too bad a trade off.
I would not be interested in the reflective fabric, even with the defect corrected, for the same reason I don't like tents made of dark colored fabrics - way too gloomy.