I guess I look at results not some idealized concept
FWIW one of the best axial rolling designs I ever flew /seen is the ZLIN526AFS
very low wing setup with some dihedral
for those who don't know the axial roll centers on the spinner and thd stab to give the optical illusion of a pure axial roll The wing location is of secondary importance.
The CAP232 is one of the , if not the best show designs going because the force setup provides for great end over end tumbles
All of em will tumble- the CAP just has the best setup for it.
Will a trainer do axial rolls ?
You bet yer asp it will - if set up right
A clipped wing Monocoupe will do the entire bag o tricks.
I can do horizon to horizon slow rolls with any wing location and the model looks to be right on "line " the spinner /cowl is your visual reference.
Now for the Doubting Thomases:
take a stick held pattern model -oneof theose little planes used to work out sequences on the ground and readjust the stick such that rolling the model either aligns the spinner or misalignes it , as you twirl the stick
It takes a litle futzing but soon you will see the alignment of the fuselage which gives an apparant perfect axial roll
(why do I do this ).