RE: What is the lightest 80 to 90 sized turbine avalable
If you are looking for something to replace a 90 size ducted fan jet, then I would look no further then the Jet Central Super Bee which is now kerostart and puts out like 15lbs of thrust, I think.
The booster 90 is a hair lighter then the jet central rabbit. From videos and personal experience, the rabbit spools up alot faster than that of the booster. The booster looks to be well made and both turbines are kerostart.
I am assuming you are looking for something in the 19-21lb thrust range and I believe these two turbines fit what you are looking for. Do you research and make a decision. Hope that helps.