We go on in the program of investigating the removal of divergences of a generical quantum gauge field theory, in the context of the Batalin-Vilkovisky formalism. We extend to open gauge-algebrae a recently formulated algorithm, based on redefinitions δλ of the parameters λ of the classical Lagrangian and canonical transformations. The key point is to generalize a well-known conjecture on the form of the divergent terms to the case of open gauge-algebrae. We also show that it is possible to reach a complete control on the effects of the subtraction algorithm on the space M gf of the gauge-fixing parameters. We develop a differential calculus on M gf providing an intuitive geometrical description of the fact the on shell physical amplitudes cannot depend on M gf . A principal fiber bundle E → M gf with a connection ω 1 is defined, such that the canonical transformations are gauge transformations for ω 1 . A geometrical description of the effect of the subtraction algorithm on the space M ph of the physical parameters λ is also proposed. At the end, the full subtraction algorithm can be described as a series of diffeomorphisms on M ph , orthogonal to M gf (under which the action transforms as a scalar), and gauge transformations on E. In this geometrical context, a suitable concept of predictivity is formulated. Finally, we give some examples of (unphysical) toy models that satisfy this requirement, though being neither power counting renormalizable, nor finite.