The SWF I have takes a flashvar parameter.
I added a addvars parmaeter to the SWF link type. Its used like so:
[[swf:flvplayer.swf|This is the title|-addvars {file http://mysite.org/xowiki/file/some_flash_video.flv}]]
I added this to the swf render_found instproc.
if {[my exists addvars]} {
foreach {name value} [my set addvars] {
append addParams "so.addVariable('${name}','${value}');\n"
}
}
And added addvars as a parameter for the swf subclass.
I still can't see the video though so I might have missed a step. I am still working on it.