But, the SIPS is not compatible with the Astrocrumb filter slide if using a Feathertouch focuser
The SIPS is 100% compatible with the Astrocrumb filter slide.
We have it installed on the SIPS in these pictures:
Like Dave said, the Astrocrumb screws into the threads on the rear of the SIPS itself; not the Feathertouch.
If your threaded nose-piece is too large, you were accidentally sent the wrong part. Call Roger and I'm sure he'll make it right. Remind him you are using the SIPS.
Installing or removing the entire filter slide takes about the same amount of time as it does to install a single filter the old fashion way:
Screw in the nose-piece, and tighten the two wing nuts on the slide.
15 seconds and you are good to go.
I'll take some detailed pictures and post them soon.