By request. I modded my machine with the things in the title. Not original on my part; the info is already all out there. But here is a condensed overview.

1. Dimmer for flow control. Image of finished mod:
userpix/101824_5960121e-28e8-4feb-9709- ... 325BQ.jpeg

Details: I purchased an AC lamp dimmer switch, the kind you find in a typical floor lamp. They are ten bucks on Amazon or eBay or whatever. Took the red wire off my pump and attached that to the black wire on the dimmer, and the white wire on the dimmer goes to the terminal where the red wire was. I soldered that connection. It works as you would wish.

To mount it, I drilled a 1/16" pilot hole then used whatever size bit works for the dimmer to widen it to the correct diameter. I drilled slowly and vacuumed the whole time, to prevent any/all slivers of metal from getting into the machine (or on the floor).

The OPV mod is easy. Simply take the overflow tube off the valve (carefully), and turn that bit out. Image below. You can see the hex area for adjustment. If your machine does not have an adjustable OPV, you can add one. Virtually any available one would do the trick.