not really sure i'm following you muebe... i don't see how the 90 degree elbow differs much from what i have at the end of mine, and if it is a bit of a sharper angle, it's certainly not by that much...
i have smoke billowing out the vents at the back of the smoke generator.
i did not get burn-back this time, but the gumminess is going to become a problem and 10-20% loss is still too much...
curious to see how hot quarlow's box leaves the smoke in the chamber... it may be easier to just use a box.
my set up has to be torn down and rebuilt every time i use it, so disposable pieces may be best anyway.