I've now acquired a Peterson Strobostomp 2, which has the capacity to program custom tunings.
The general opinion for lap steel is to flatten the major 3rds and 6ths by between 10 and 13 cents, and sharpen the 5ths by 2 cents or so.
I've employed the tunings recommended by John Ely (which isn't as extreme as some tunings):https://www.hawaiiansteel.com/tunings/my_tunings.php
I am using A6 and E13 by the way.
This has made a real difference, and has reduced slight dissonances in most positions, especially playing the 3rd and 5th.