As for the .25 cal conversion, I am working on that.
As for the barrels on the Hubens sold by me, they are Lothar Walther.
CZ vs Lothar useage on bullpups, Interesting side note:
I was at the IWA show in Germany 2 weeks ago and visiting the booth of a very well known bullpup manufacturer from Eastern Europe. When I brought up the fact that their bullpups were known for their accuracy, and I attributed it to their use of CZ barrels, he pointed out to me that they will also use Lothar Walther barrels. They detected no difference in accuracy between CZ and LW.