Take a look at this:
http://insane-gamers.com/showthread.php/9462-SOLVED-www.beyond.lt
That server uses kasha protection, with my system folder both walker and l2net works with no tools.
Did you try deyoda? Worked for me on 10.8.6 at least
http://ftp.bspu.unibel.by/pub/Tools/ARC/w32exe/deyoda12.zip
Other easy way to get rid of the file size error is to pad the l2.exe file with empty data until it gets the correct size.