An effort is made to reduce the errors of continuum solvation models (CSMs) with semicontinuum modeling to achieve 3 kcal mol(-1) agreement with experiment for acid-catalysis activation Gibbs energies. First, two underappreciated CSM issues are reviewed: errors in the CSM solvation Gibbs energies grow beyond 5 kcal mol(-1) (i) as ions are made smaller and (ii) as water clusters grow larger. Second, the computational reproduction of the known Gibbs energies (Delta(r)G and Delta(double dagger)G) of the paradigmatic reaction ethene + H2O + H3O+ -> TS+ -> ethanol + H3O+ is attempted. It is argued that, despite the >5 kcal mol(-1) solvation errors for ions, it is possible to employ error cancellation strategies to reduce the errors in the reaction and activation Gibbs energies to 3 kcal mol(-1) accuracy. A new 3 kcal mol(-1) effect due to solvent-molecule "placement" (confinement from 1 M bulk concentration) was isolated and proved useful. Third, computational reproduction of the known entropies (Delta S-r and Delta S-double dagger) of the paradigmatic reaction is attempted using Trouton's constant and neglect of solvent structure reorganization effects (which must cancel well for this reaction); this worked well for Delta S-r but needs empirical correction of similar to 11 cal mol(-1) K-1 for Delta S-double dagger due to solvent disorientation when H3O+ is consumed. These entropy estimates allow for enthalpy (Delta H-r and Delta H-double dagger) estimation from the Gibbs energy values. Fourth, two recommended options, including A + H3O+center dot 2W -> [AHOH(2)(+)center dot 2W](double dagger), are shown to also work well for the activations of propene and isobutene.