Your comments about stability are fine - -all basic rules of stability.
What these guys are doing -having seen it and discussed the issues at length, is trying to improve stability with aft cg locations.
A contradiction in basics.
The std "trick" is to add some effective downthrust -which must be contradicted by adding elevator trim.
Some do this by adding incidence to the wing -which results in the fuselage now flying angled up a bit higher at the tail
This then needs a bit of elevator/stabilizer trim to compensate
The angles between thrust,wing and tailplane have now changed .
Thrust is now "pulling down" as wing "pulls up" and hopefully the whole result is a plane which "locks in" better to straight flight-even tho cg is aft.
Does this really work?
some guys swear by it .
IF -we have forces working against each other, we can create a more stabilized arrangement . That much is fact.
The energy required to keep this new setup moving must have increased -tho it is slight - as is the difference in stability.
If you have flown competitive aerobatics and or speed models - this stuff is all familiar to you . If not - it likely sounds just plain ol weird.