Hi again Mori,
" I am not 100% sure, but the current firmware ver. 1.08 (probably) does not support the WSPR-15 mode."
I was wrong, WSPR-15 was supported from ver, 1.06. Sorry about that.
So you need to go for WSPR-15 if you want 6 character grids.
73 from
Geir, LA6LU