Wish it were so, Akira. I do have the 800/8 ED lens head though, which is even more elusive. Very very sharp and very very cumbersome to use.
It is a long-focal not telephoto design thus the overall contraption is nearly 1m long and heavy. Using it demands the very best of tripod support. Funny this came up as I retrieved the lens head from its storage yesterday and set it up for use wih the PrimaLuce Z5 today (or tomorrow, my plans involve a more conducive weather than at present).
I do own the 1200mm f/11 ED-IF, which is much smaller and lighter.