I've done a sh*tload of research regarding this in the last few days. I've read tons of documentation and research which all seem to be consistent with eachother, including that aspirin has proven to have very little, if any, effect on fat loss results. Tests with E + C, vs only E, vs only C, vs E + C + A. etc. etc. humans, mice, different variables: including exercise routine, obesity, age, diets.
I can post some webpages if you're interested.
Another interesting thing I read was that if you imagine a bell shape curve on an X and Y graph, the perfect ratio (peak of the graph) was 1:10 <20 mg E + 200 mg C> 3 x a day. Nothing less, nothing more ratio wise.
But yeah, aspirin is risky within itself and the most important part of the stack is the combination of the caffeine + Ephedrine dosages. If you do some google searches you'll find that most forums/reports have dropped the A out of the stack.