Maybe really push the envelope and only mash for 10-15 minutes!? Just as soon as most of the starches turn to sugars that can be measured by refractometer as approaching the pre-boil OG that you'd anticipated, call it good and start the boil. Might happen in as little as 10 minutes?? For example, say you wanted a pre-boil gravity of 1.040. Using refractometer, you can easily test for this every 3-4 minutes if you want. Then just as soon as you get close, like 1.038 or so, immediately end the mash / heat 'er up to the boil. What happens to body of the final beer if you do that?? I have my hypothesis!!!