@scm698 thanks, that's perfect!
@keyman I re-configured kgroup 1 in the same order as before (found by experimentation) but adding the two last keys, and kmapper 2 just like the scripts that come with the software but adding two keys.
Here's a complete script that seems to work for me, sorry for the bad form with all the individual hey lines, I just copy-pasted what I tried out in commander.
description
Use all 18 keys.
script
kgroup 1 hey clear
kgroup 1 hey k 1 add
kgroup 1 hey k 2 add
kgroup 1 hey k 3 add
kgroup 1 hey k 4 add
kgroup 1 hey k 10 add
kgroup 1 hey k 11 add
kgroup 1 hey k 12 add
kgroup 1 hey k 13 add
kgroup 1 hey k 5 add
kgroup 1 hey k 6 add
kgroup 1 hey k 7 add
kgroup 1 hey k 8 add
kgroup 1 hey k 14 add
kgroup 1 hey k 15 add
kgroup 1 hey k 16 add
kgroup 1 hey k 17 add
kgroup 1 hey k 9 add
kgroup 1 hey k 18 add
kmapper 2 hey clear
kmapper 2 hey k 1 add
kmapper 2 hey k 2 add
kmapper 2 hey k 3 add
kmapper 2 hey k 4 add
kmapper 2 hey k 5 add
kmapper 2 hey k 6 add
kmapper 2 hey k 7 add
kmapper 2 hey k 8 add
kmapper 2 hey k 9 add
kmapper 2 hey k 10 add
kmapper 2 hey k 11 add
kmapper 2 hey k 12 add
kmapper 2 hey k 13 add
kmapper 2 hey k 14 add
kmapper 2 hey k 15 add
kmapper 2 hey k 16 add
kmapper 2 hey k 17 add
kmapper 2 hey k 18 add
all join
eigenbrowser vertical nudger 1 un connect
eigenbrowser tapper 1 un connect
eigenbrowser vertical nudger 2 un connect
This configures a layout like the standard layout with groups of four keys, plus the two last ones. The other layout scripts that come with the software don't work because they don't include the two last keys, but it's straight forward to fix them, just add keys 17 and 18 to them.