As I mentioned elsewhere, I have been modding my Lee pot. Hopefully the photos will help.
First thing was to make a new base plate. The aluminium sheet I had wasn't thick enough by itself, so I added a couple of flat steel bars underneath on either side. The support plate for the pot was made from three pieces of flat steel bar welded together and then cut and ground to shape. I figured that having steel in contact with the bottom of the pot would eventually cause rusting, so I cut another piece of ally plate to fit between. The extra holes are to allow for the existing screws on the bottom of the pot, as I didn't want to remove them.
The support rods are 10mm x 1.5mm thread (because that's what I had. I was originally going to use 1/2" rod, but I don't have a 1/2" tap to thread the base plate!). It took a lot of trial-and-error to get the support plate to fit, as every time I tightened it up gaps would appear at the front. Eventually I realised that the element mounting screws were actually holding the pot at an angle, so I filed about 1/16" from the bottom front of the main tower. This canted it forward enough that the pot now sits pretty flat on the support plate.
I made a rod to replace the original long support rod. This was only long enough to go from the bottom of the pot and extend about 1/2" at the top. I silver soldered a nut on the bottom of the rod, ground it down to form a head, turned a shoulder on the top bit and ran a 3/16" thread down to hold a bracket for the thermocouple probe.
A mold shelf was made from more ally plate. (I might add a guide later).
Next was an aluminium knob screwed onto the top of the metering rod, so I don't need a screwdriver to adjust it.
Then it was time to try it out, using my spare, untried el-cheapo (REX C100) PID.
It worked well, inasmuch as it heated up very quickly (I didn't have the PID in cct to start with, and it got up to nearly 1,000F before I realised what was happening!!!!).The PID itself worked well and kept it to within 2 degrees of the target temp (725F) once it had settled down - and I hadn't even run the auto mode (mainly 'cos I forgot how to set it (Chinese instructions!)).
As for casting, definitely not as straightforward as the Pro-Melt. The flow rate is trickier to control, and I ended up with lots of "run-off" on the mold and a very poor success rate. I put this down to the rounded shape of the metering rod at the nozzle, and when I adjusted it to try and give a smaller flow the rod didn't always drop back to seal the nozzle and it kept flowing!! If I make a new handle on top from steel, instead of ally, the extra weight, directly over the nozzle may fix this. I'm also wondering how difficult it would be to make a new handle assembly similar to the Pro-Melt's - the extended handle and the pivot at the top of the metering rod are more positive in operation.
All things considered, though, it's not bad. I'd like to make a replacement nozzle and metering rod, with a better shape for controlling the flow, but that will be a last resort! In the meantime, I'll continue to experiment with it.