Here is a test you might want to take into account. I own an HGC-320-700A SMPS which only allows for maximum current trimming, but output voltage is fixed. In order to avoid unnecessary heatsink, I will suggest using an RC before the Swenson where the R is a big Alu clamped wirewound resistor bolted to the chassis. Just leave 50V for the regulator which may dissipate a lot anyway depending on the output current.
There is no caps below and was stable enough. I could have added an output cap but I didn’t on this test. You can see how all the HF noise is trimmed out! About 40 to 60dB 🙂
The 44mA and 88mA traces are the SMPS feeding the power resistor directly.
This can be improved further with a (mandatory) output cap. A nice 30uF oil cap should do well.
I have offered some pairs built and tested to builders using the prototype boards. I may do a couple more if you are interested