this */
     */
I tried
how can I

Does the workstation you're using have hardware cursor support?  Or does
the server generate a software cursor.  You can generally tell the difference
just by using it.  If the cursor blinks a lot when there's screen activity,
it's probably a software cursor.  If it has a hardware cursor, I think you're
probably battling a bug in HP's X server.  I'm not familiar with any hardware
cursor chips that display cursors greater than 64x64.  It's quite possible
that the server is just echoing your preferred cursor size without actually
checking it.  I vaguely recall that very old MIT server revisions did just 
that.

In reality you're probably stuck with a 64x64 maximum size cursor regardless
of what the server returns.