Given the 5 ohm / 0.3mV Aidas with a SUT first stage it would be typical to start with a 1:20 which gives you ~117r load. But its all very preamp dependent and system gain dependent.
Nagra lists VPS transformer input gain at a low 11db ( must be a 1:4 ?)
One of my clients with a Zesto has landed on ~300r, meanwhile RADA just created a 1:40 SUT to demo with, using an Aidas cart ( AU- CU model @ 3.5 ohms ) resulting in a 40r to 60r load depending on phono input r on their preamp ) with great results.
Looking forward to hearing what you end up preferring
