I have both these substances arriving in the next week and was planning on testing the combo, so I'll report the results when I do. Purely speculating here, but if I had to guess I'd say the reason that Dexter and Aphex had different outcomes is that the former dosed 4-FA 2 hours after the 2-FMA, so the 2-fma was still fully active, whereas Aphex waited for the 2-FMA to drop off before dosing 4-FA.
This would hold true to my experiences with 4-fa, which have shown me that if you wait to come down to redose (i.e. redosing after 4 hours) then the second dose will be ineffective, whereas if you redose when you're peaking/plateauing then the redose will most likely have the desired effects. Again, just speculation here, but I'm pretty sure I'm right.
All this being said, I'm a little skeptical about this combination, mainly because for me, 4-FA alone acts on dopamine about as much as I can imagine a recreational substance doing so, and the level of DA release from the 2-FMA sounds more preferable for task completion. I still plan on experimenting with these though, mainly because I'm curious what the simultaneous actions of a 5-HT and a DA releaser will feel like.