Thanks, glend, for posting!
I got interested and googled. Found a review for their 153mm f/6, 3kg (but Zwo also has faster newts):
http://escope.de/english/zw153/2/
he speaks of probably not being able to mount heavy photo equipment rigidly enough.
now, this model in the review apparently was bought 3 years ago.
Possibly, Zwo has altered their design.
*****
Clive
****