i went extremely high with the t3, this is true. didnt eat more fat, but did get in the way of muscle building. dont recommend it.
human grade t3 is very cheap and easily accessible online.. just google it
I have debated this 1000 times and what you wrote about t3 causing a permanent metabolism increase is actually the exact opposite. I know one guy that is fat all the time after being lean for nearly 3 years straight and he said t3 fucked up his thyroid and now his natural look is fat and blames it on t3. A lot of people are actually saying this.
As for T4 a lot more easy to control, however the bodybuilders I know do not just do t4 alone but always do both t4 and t3 and claim it is better then just doing t3 alone as t3 can be hard on your system, this way you can do t4 and only a small amount of t3 instead of a lot of t3 at once.
Remember T3 is the stronger one and T4 the weaker, not knowing this can be a costly mistake. Personally I never take either, why bother when ECA is better and acts as a stimulant, a suppressor, a fat- burner and much much more. Why not use something that you get a lot more out of and has NO long term effect. And yes t3 can cause permanent changes and ECA does NOT