Two suggestions based on the fact that I built many of these over the years. Use the 16 gauge. Yes it’s a little more expensive, but sounds more complete top to bottom. More foundational weight and body to the music with slightly improved mids. Better sense of ease. 20 gauge will trick you into thinking they are a tad more detailed, but your brain thinks this because some of fullness and body is missing. You will only notice this after direct comparison over time.
Also, use KLEI Absolute Harmony RCAs. They are better sounding than Duelund. More resolving with better inner detail and realism. Make sure the builder cleans the freshly stripped wire with Isopropyl alcohol as the strands will have dried oil on them that should be cleaned before soldering.
Parts Connextion will build them for you. A couple of sellers on USAM also make these as I recall.