I bought a pair of Alphaflys when Dicks had them on sale for $90 in November. I'm going to run a marathon this spring. I've been doing all my training runs in trainers that aren't designed to run fast (Brooks Ghost and Glycerin). My marathon pace in those shoes seems to be about 8:20-8:35, if I had to select a pace I'd say 8:27; most of my long runs are between 9:30-10:00, with the average being 9:45; tempos are in the low 8 minute pace range; when I do mile repeats, I'm in the 7:30s). I know there's a difference between efficiency and speed, but if they make you 4% more efficient than my Brooks shoes that I can run 8:27 in, then that'd be 8:07. My question is does efficiency translate to speed, if not, what should I aim to run my upcoming marathon at? In the back of my head, I think I can run sub 3:40, but I also don't want to blow up. The one time I ran in my shoes, 6:50 pace felt easy, but it was a short run.