Cone wrench for freehub body?

The new rear wheel was supposed to have the usual 10mm Allen inside to
remove the freehub. Said the dealer. However, when I lubed the bearings
I saw none of that, just a much bore hole with wide long splines deep
down in there (of course I forgot to snap a photo ...). I wrote to the
dealer and now they say I'd need "some specific sized cone wrench".
Could not find much on the Internet and I wouln't know how a cone wrench
could possibly be used.

Does anyone know of an alternate mounting system versus the usual 10mm
hex? If so, can that still take Shimano freehubs?

The main raason I ask is that freehubs only last 5000-10000mi with me.
Lots of hills, heavy loads. Having to throw out the whole rear wheel
would be sad.

--
Regards, Joerg

http://www.analogconsultants.com/