Has anyone determined their own average stem/tube weight and compared this to others?
This has been discussed in the PD thread. First, you can't get accurate measurements on this unless you've got a good scale that's accurate to .01g. Then you have to load multiple bowls (I used 10), weigh the total amount, and divide by the number of bowls you've loaded and weighed. And how fine your bud is ground is a factor. I can get .05g as an average if I use dry, fine ground (almost powder) and pack pretty tight, but after doing multiple tests like this I think .025-.03 is a more normal average. If your bud is high quality and sticky, your average load is going to be less than with dry, mid grade (and should be).
This vape (and the Zap or Eterra), with the small, easy to cap off bowl, is easier to measure for load size than most, but since a full tube can still vary by 100%, depending on what you're loading and how, it's still not a good idea to put out a number, as far as saying 'this is what you get in a bowl'.