An inherent inefficiency in the Anvil design is the large gap between the basket and the side wall of the unit. The water trapped in this area has very little sugars which have diffused from the bottom of the kettle. On my 6.5 gal Anvil, this amounts to 2.9 liters of water which is not directly involved in solubilizing starches and the subsequently produced sugar. I typically mash with about 15 liters of water, so that would make it around 19% of the water added is not used in the mash. I can only guess at the volume in the 10.5 gal Anvil, but it will be close to proportionally the same.
Having measured the gravity of the water alongside the basket versus the wort which is recirculated and in the mash basket a couple of times, I decided to lift the mash basket about halfway through the mash and then again just before mash out to mix this water trapped on the sides of the basket into the active wort.
I was getting around 83% mash efficiency (I do full volume/no sparge mashes) and increased that to 86% to 88% on my last four brews trying this new method. It is a bit more work and still have some additional work to nail down the process to get it a bit more consistent, but it does make a noticeable improvement in extraction efficiency.