Thanks for infoI'm thinking about my next hombuilder project for the hard way of scratch building
I have extensive work experience in composite materials and aeronautical wood construction (HiMax - Pionner 200 - Atec Zephyr).
So I prefer the wood-composite system, but I have no problem with a steel tube fuselage. I discard aluminum sheet for now.
My flight experience is in 3rt generation ULM (450 kg).
Weight limit 550 - 600 kg but always in the lowest part of the range,
If you are planning to make this type of airplane only for yourself, than feel free to make some unusual construction. However I suggest to think also about registration, basic strength testing (requested for registration) and possible future re-sale. I personally would be a bit conservative with design. tandem wings, canards.... OK, probably interesting, however majority of pilots will speak about new shapes and configurations and fly with standard looking plane.
You mentinned three projects.
"Michael Barry Sourisce Bulle
KR2 with motorsailer wings
I personally like Piuma.
If you want to "play" than think about to remove struts = re-design wing to self supporting version of wing. You can also increase wing span a little bit. 13 m wing span is OK, 15 m would help you to decrease power requirements for horizontal flight.
Piuma wing look a bit like wing used on ultralight Tukan / Duo Banjo And if I have good info than latest version Tukan wing has been also re-designed to remove wing struts.
Also... Piuma could be relatively easily converted to electric propulsion system.
So that is my personal point of view