Martin,
Been digesting all this, thanks for posting.
The first article mentions the IRCA (International Radio Club of America) which is primarily a MW DX club. So, my guess is that much of what is presented there is optimized for the AM BCB.
My antennas with 9:1 ununs using 43 material work great on LW and MW but start to go deaf much above 80 meters.
Have not had much luck here with powdered iron material for LW/MW but built an antenna with a unun using T106-2 and it worked well on 40 meters and higher frequencies.