Short of soldering up a jumper cable, is there a way to get Precision X1 to properly output the right PWM signal even if it can't read a tach signal?
 
Background:
I currently have a hybrid kit on my 3080 ti and there are 4 fans I'd like to control for the radiator, so I have them going through a fan hub. The hub's control cable (4-pin) goes back to the hybrid kit's "fan 1" splitter cable that normally goes to the rad-fans, but I have different fans with different RPM ranges, so I just want PX1 to output the duty cycle to the fan hub based on temperature. When I hook it all up, PX1 says what % it should be driving based on the current temperature, but the fans run at 100% the whole time. While in BIOS (pre-windows), the fans run at a lower speed, so it seems that it is PX1 setting the fan speed at max. I also tried to not use a curve and just use the sliders to fix a %, but it didn't work. If I plug the hub into my motherboard and set a fixed speed (65% for example), it does that perfectly fine, but I can't use GPU temp from my motherboard's fan header.
 
My current plan is to make a splitter cable that passes all lines from one of the EVGA rad-fans to the hub, but splits the tach-line off to a separate fan plug. Then I'll plug the fan hub's plug into the GPU's splitter cable that doesn't have the tach line and the tach-cable over to the splitter cable that does have the tach line. Rudimentary sketch:
 
Is there a way to get PX1 to drive the fans correctly without adding the DIY tach-splitter cable?
 

I tried both options and the second one seemed to mostly work, but it was a bit intermittent. Seemed like the hub fans would sit at lowest speed and not change. I wiggled the connector and they started following along with the fan directly plugged in. I thought "oh good it's working", put my side panel back on, and it stopped working.

Also, plugged in to aux fan connector on the gpu before trying my second sketch above and that did the same thing as before, full speed fans. I have read that it should have showed up as "fan 4", but no fan 4 showed up in px1, even after rebooting the computer. Does px1 need to be reinstalled to get this to work or could it actually just be a loose connection between the hub connector and two different fan headers? It always works fine when plugged into a motherboard header, so I'm not sure why it would be acting so weird on either gpu fan header.

I know the hub connector doesn't feed back a tach signal, so I'm guessing that would make the gpu not see that there's a "fan 4" connected, but I am only guessing. I came up with one other idea that doesn't require custom cables, but it will only work based on the specific way I've hooked my fans up (see mods rigs section post in signature lol). I can just run the evga fans on the "fan 1" splitter cable and the other two fans (which are quieter) on a different constant signal not controlled by px1. Not ideal, but it should be tolerable and still better than just running all the fans at ~65% forever regardless of load.