When I use 80% of my speed in F2L, my solves are, well, 80% as fast as when I use 100% of my speed. (Actually, probably more like 90%.) My lookahead simply doesn't improve when I slow down. I don't know if that means my lookahead is really good or it's really bad (probably the latter), but either way, it just doesn't improve for me at all when I slow down.
For me, closing my eyes while solving each step (to train me not to watch the pieces while solving them) has really helped.
Mike, I think you make some good points here. I'm guessing that perhaps you are the kind of speedsolver where the fast-and-choppy approach would be a better goal to shoot for. One of the things that stands out about watching Macky solve in person to me, is that he does have pauses between pairs and steps. However, those pauses are not that long, and his turning speed is ridiculously fast which makes up for it. Sort of like Daniel Beyer as well
One thing that works very well for me, and I'm directing this to anyone reading this not just you personally, is to not so much
think about looking ahead, but to just go a bit slower so that my brain does it for me. I don't know if that even makes any sense, but that's how I feel. On really good averages for me, I feel like I get my turning pace juuuuust right so that the pairs present themselves to me, I don't go looking for them. I don't feel as if I am actively trying hard to look ahead, but it's as if the pairs just jump out at me.
Dan Knights would strongly disagree with this, he always advocated to really actively try very hard on every solve to look ahead. I've found that actually trying to look ahead stresses me out too much, and my solve time suffers. If I don't try very hard at all to look ahead, but focus on finding the right pace for doing so, then the pairs just present themselves to me. I don't know of any other way to describe it, but it is how my best solves feel in mid-solve.
Chris