Yeah, I'm around 10 SPL in a 20 yard pool and I can work it down to 8 SPL under minor speed sacrifices. (I can also work it down to 7, but that looks ridiculous and is much slower).
I've taken away some very good help from this discussion:
1. The risk of "overgliding" is real and everybody tends to overglide when trying to minimize SPL. I'm still not 100% sure how to notice, that you start "overgliding". Coach Stuart, what exactly do you take into account when optimizing (not minimizing) SPL? Is the biggest part of it that it "must feel fluent"?
2. The "green zone" from Coach Stuart is a really good target area. Of course it's only a zone and you might be in the upper, middle or lower part of the zone. However, chances are darn good, that your optimum is within this zone.
Another thing, I'd like to add and ask:
When reducing SPL at constant pace, most of your changes in technique will be good changes and contribute to higher efficiency. However (and that's kinda confirming what Tom was experiencing, too), given a certain skill level, there are a couple percent (let it be 2%, maybe 5%, idk) that you can gain at very high costs:
1. Overstretching your entire upper body while spearing: a longer body line helps, but "overstretching" is strenuous.
2. Pulling stronger (and therefore faster) than would be natural.
3. "Overstretching" your ankles, i.e. stretching them more than your flexibility comfortably allows.
These are all examples for "optimizations", which are not energy-efficient, but will improve (increase) your pace/SPL ratio (assuming that balance and streamlining is already quite advanced). My question is: where's the sweet spot? How do I find out "how much" of these three things I should incorporate? That's a non-trivial optimization-problem to me. What do you guys think?
Simply taking perceived exertion sounds a little too error-prone to me.