In a similar vein I also stumbled upon a coincidence of dimensions when I was browsing through my local Sur La Table store. In this case it was a standard canning funnel, which turns out, just like your PVC fitting, fits perfectly inside the throat of the Super Jolly.
Adding to the dimensional coincidences is that a standard tamper also fits perfectly inside the throat of the funnel. This is due to the thinness of the funnel - any thicker and it would not work...
http://www.flickr.com/photos/akatayama/177090940/
The "freebie" plastic tamper is kept in the funnel as I pour in one shot's worth of beans. Doing so allows me to make last minute adjustments to the grind without the beans getting in the way. Then I start the SJ and lift the tamper to let the beans in. I then rest the tamper onto the beans during the grind, maximizing stability and improving feed by its subtle weight.
Even with my rather heavy 20 g standard dose, all the beans comfortably fit into the throat of the funnel, meaning that no beans gets trapped behind the tamper during grinding.
Once I saw that the tamper fits into the funnel, I decided that I might possibly use it during dosing and leveling, resulting in a 100% use of the grounds. Great - much cleaner and no waste! (I pre-measure my beans before grinding ...)
http://www.flickr.com/photos/akatayama/177091602/
So after grinding I move the funnel from the grinder and into the portafilter. With the funnel resting inside the portafilter I lightly knock the sides of the funnel with the plastic tamper to loosen any stuck grounds and superficially pre-tamp just to get the dose below the rim of the portafilter.
After this superficial pre-tamp the funnel gets used for yet one more purpose - as a tamping base!
For this I invert the funnel so that the small end points up and rest the portafilter into its throat. The wide end of the funnel creates an incredibly secure base, and the strength of the stainless steel allows me to use the hardest of tamps without a worry. This last use of the funnel works particularly well with both a naked portafilter or with a single-spout portafilter, both of which can be awkward during tamping.
I imagine the PVC fitting can be used in much the same way, except its thickness probably precludes getting the tamper to fit inside.
A video of the entire process:
http://youtube.com/watch?v=D_BEnIr07G4
BTW speaking of "Home Depot" Super Jolly hacks, here's one I did using the black PVC drain fittings found in the plumbing department:
http://www.flickr.com/photos/akatayama/133241695/
I removed the stock doser and my SJ is now doserless! Grinding directly into a bowl greatly simplifies the process and allows for catching all of the grounds...
