Increasing the fuselage length increases the polar-mass-moment-of-inertia (increased resistance to rapid changes in direction). I would expect the straight-fight to be "smoother", and the spins and snap-rolls to be "lazier" and less dramatic. (for me that would mean less "fun", cuz I like doing dramatic spins and snap-rolls)
With the low-wing configuration, the designed amount of dihedral has probably been incorporated to avoid roll-coupling when rudder is applied. (A low-wing pattern plane typically requires about 2 degrees of dihedral at each wing-half.) Accordingly, one can maintain knife-edge flight with the application of only the rudder. If you reduce the dihedral you will probably induce adverse roll when rudder is applied (i.e. right rudder => left roll; left rudder => right roll).