Gravmag 9s for QB78 series?

[dukemeister]

A recent post here got me thinking about Gravmags, and can they be used on my QB78 types. Seems to me I had problems installing the Gravmag 9s on my 78 a few years ago when I first got into the Gravmags, and the generic Thingiverse knock offs. And I did find some modified .stl model files I was working on to try to get the printed ones to work on the 78, but I gave up on it. Well, I just did a search on Google and found a Youtube of someone who shows a Gravmag 8s installed and working on a Beeman Chief, which I believe has the same breach as the QB78 series. One commenter below the video says they tried it on a 78 and the pellets didn't feed, which is what I remember happened to me. So, has anyone here tried to put a Gravmag multishot on a QB78 type, and if so did it work?

[dukemeister]

I can answer my own question, sort of. I pulled out one of my home printed 2240 multishot devices and it was very obvious the main issue is it is not long enough for the QB78 breach opening. The slot in the 2240 is pretty square and short, whereas the slot in the QB78 is longer and tapered at the rear. Consequently, the dovetail has only about 2mm length to catch at the rear. My printed magazine holder broke on installation at the dovetail ear, it's a weakness of the home printed version - inter-layer adhesion issue plus a very thin section, plus a screw hole  = no strength. I had a quick look at my old stl model to adapt this to the QB78 and it was clear I had already attempted to make a version to work .. the length of the mag was increased and the dovetail ears had been strengthened... I completely forgot having done this ... it was about 2 yrs ago... old age is *(&^ as they say. Anyhow I have revamped this project and it it works I'll post an update. 
My biggest complaint with the QB78 series is the lack of a repeating breach, so if the gravity magazine system works, that will likely bring mine out of the closet for some fun shooting.