I think it would be too rounded to get a definitive seal from nozzle to tube
You should copy the one VacLab already built. I asked him before several months ago and he said it was OK to do it, but you can ask him again if you want.
His works pretty good, and he seems to get pretty definitive results with it. Good luck!
[MEDIA=youtube]DS-UopxPqiA[/MEDIA]
I have seen people making similar things for vacuum-forming plastic hobby projects, nearly the exact same construction - so it seems like a similar concept - just going the opposite way when you are testing with vacuums.
https://s3.amazonaws.com/assets.flitetest.com/article_images/full/pic7-jpg_1412404560.jpg
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