Bertrand
This is a relatively new feature I think. The syntax you
experimented with in your earlier post seems reasonable.
http://article.gmane.org/gmane.comp.gis.therion/2912/match=splay
At least no errors are reported.
However I just experimented with both .lox and .kml outputs.
It seems that splays are generated regardless of whether splay-shots
are enabled or disabled for both of these formats.
I think this feature needs some more development work :)
Bruce