No worries! I think this discussion would be good for everyone on the board to see.
My main point was that there's, unfortunately, not enough research and human data on the hundreds of dietary supplements. This is one of the reasons the FDA has to formally prove an ingredient is unsafe before they can pull it off the market - and that's what my last paragraph was getting at. Because the reality is I don't think many supplement companies can fund a large scale clinical study to prove your specific formulation is safe and effective. Ideally it'd be great, but realistically it'd be near impossible.
And to address some of the DMAA safety issues two good reads can be found here:
Toxicity section from PubMed:
https://pubchem.ncbi.nlm.nih.gov/compound/1_3-Dimethylpentylamine#section=Human-Toxicity-Excerpts
Merck Index entry on DMAA (need a subscription) :
https://www.rsc.org/Merck-Index/monograph/m7427/methylhexaneamine?
But the important part from the second source is essentially "No long-term toxicity studies are in existence, although acute LD50 of DMAA has been established at 39mg/kg bodyweight intravenous injection and 185mg/kg bodyweight intraperitoneal injection. Theoretically well below what can be achieved via oral ingestion."
It's unfortunate the oral ingestion is theoretical, but let's just assume a 90kg (200lb man), he would need to IV 3500mg of DMAA to reach LD50 levels and this is many times lower than that of oral ingestion. This is why we believe 120mg/serving can be safe if used responsibly.