I've got that wheel with a 383L+ and 1.25" filters
I am connecting to the camera with a male to male T adaptor, one with short threads on both sides, so there's only about 3mm between the camera and the filter wheel.
I can't claim to have absolutely no vignetting (at F/6.25) but the amount I see is tiny and only affects the far corners of the CCD. A flat will cure it. It's good enough for me.
Chris