What Barlow lens for mini zwo for Coronado PST imaging

[Elp]

What Barlow lens are people using with a mini zwo camera to reach focus with a Coronado PST? I've got a meade 2x telenegative but the thread diameter is the same as the OD of the tube extensions so can't screw in that way. My other Barlow has a female thread so that's no good either.

[Same old newbie alert]

With mine I use a cheap skywatcher x2 and remove the lense part and pop it into the 1.25 barrel, then the camera

[Elp]

You don't screw the lens onto the end of the camera?