Figured there are likely people here who have not seen my modded machine in the other coffee spaces.
I’ve been into specialty coffee for a few years now. Had a GCP and sold it, along with several other machines.
Saw the rise in Arduino based pump control on the GCP machines and had a wild thought.
That was “Since most people prefer a declining pressure/flow profile, this can be done mechanically, no programming needed”.
Use a cylinder with a piston inside and spring on top of the piston. This cylinder is connected inline between the pump and the boiler.
Separate the brew group solenoid from the pump circuit so it can stay closed while the pump runs, filling the spring piston chamber. Open the solenoid to start the shot.
Add a valve to the line branching off going to the cylinder, allowing straight pump shots and steam pressure to build.
So I ordered some 316 stainless and other parts.
Machined a cylinder, piston, and end caps.
Decided I would have more room to mount the cylinder if I rotate the brew group 180 degrees (still locks in like normal) which moves the solenoid and inlet hose around to the front of the machine.
While at it, I bored out the inlet path as well as the solenoid itself, allowing more maximum flow. 
Cut a Polycarbonate lid for it and put it together.
Tested it for a bit and planned more modifications..
