diff --git a/src/ace1_compat.jl b/src/ace1_compat.jl
index 1a684b53..b6ddb839 100644
--- a/src/ace1_compat.jl
+++ b/src/ace1_compat.jl
@@ -155,9 +155,19 @@ function _get_all_rcut(kwargs; _rcut = kwargs[:rcut])
 end
 
 
-function _rin0cuts_rcut(zlist, cutoffs::Dict)
+function _rin0cuts_rcut(zlist, cutoffs::Dict, kwargs = nothing)
+   function _get_r0(zi, zj) 
+      if kwargs == nothing 
+         return DefaultHypers.bond_len(zi, zj)
+      elseif kwargs[:r0] == :bondlen
+         return DefaultHypers.bond_len(zi, zj)
+      elseif kwargs[:r0] isa Number
+         return kwargs[:r0]
+      end 
+      error("Cannot determine r0($zi, $zj) from the arguments provided.")
+   end 
    function rin0cut(zi, zj) 
-      r0 = DefaultHypers.bond_len(zi, zj)
+      r0 = _get_r0(zi, zj)
       rin, rcut = cutoffs[zi, zj]
       return (rin = rin, r0 = r0, rcut = rcut)
    end
@@ -166,18 +176,23 @@ function _rin0cuts_rcut(zlist, cutoffs::Dict)
 end
 
 
-function _ace1_rin0cuts(kwargs; rcutkey = :rcut) 
+function _ace1_rin0cuts(kwargs; rcutkey = :rcut, rinkey = :rin) 
    elements = _get_elements(kwargs) 
    rcut = _get_all_rcut(kwargs; _rcut = kwargs[rcutkey])
+   if kwargs[:rin] isa Number 
+      rin = kwargs[:rin] 
+   else
+      error("Cannot read rin; please provide a number of file an issue if a more general mechanism is needed.")
+   end
    if rcut isa Number 
-      cutoffs = Dict([ (s1, s2) => (0.0, rcut) for s1 in elements, s2 in elements]...)
+      cutoffs = Dict([ (s1, s2) => (rin, rcut) for s1 in elements, s2 in elements]...)
    else
-      cutoffs = Dict([ (s1, s2) => (0.0, rcut[(s1, s2)]) for s1 in elements, s2 in elements]...)
+      cutoffs = Dict([ (s1, s2) => (rin, rcut[(s1, s2)]) for s1 in elements, s2 in elements]...)
    end
    # rcut = maximum(values(rcut))  # multitransform wants a single cutoff.
 
    # construct the rin0cut structures 
-   rin0cuts = _rin0cuts_rcut(elements, cutoffs)
+   rin0cuts = _rin0cuts_rcut(elements, cutoffs, kwargs)
 end
 
 
diff --git a/src/fit_model.jl b/src/fit_model.jl
index 24ca1b13..c830fb57 100644
--- a/src/fit_model.jl
+++ b/src/fit_model.jl
@@ -14,8 +14,6 @@ export acefit!, assemble, compute_errors
 
 _get_Vref(model::ACEPotential) = model.model.Vref 
 
-__set_params!(model::ACEPotential, coeffs) = ACEpotentials.Models.set_parameters!(model, coeffs)
-
 default_weights() = Dict("default"=>Dict("E"=>30.0, "F"=>1.0, "V"=>1.0))
 
 function _make_prior(model::ACEpotentials.Models.ACEPotential, smoothness, P)
@@ -163,7 +161,7 @@ function acefit!(raw_data::AbstractArray{<: AbstractSystem}, model;
    coeffs = P \ result["C"]   
 
    # dispatch setting of parameters 
-   __set_params!(model, coeffs)
+   ACEpotentials.Models.set_linear_parameters!(model, coeffs)
 
    if haskey(result, "committee")
       co_coeffs = result["committee"]
diff --git a/src/models/calculators.jl b/src/models/calculators.jl
index 4019567c..0904d359 100644
--- a/src/models/calculators.jl
+++ b/src/models/calculators.jl
@@ -54,6 +54,17 @@ function set_parameters!(V::ACEPotential, θ::AbstractVector)
    return set_parameters!(V, ps)
 end
 
+function set_linear_parameters!(V::ACEPotential{<: ACEModel}, θ::AbstractVector)
+   ps = V.ps
+   ps1 = (WB = ps.WB, Wpair = ps.Wpair,) 
+   ps1_vec, _restruct = destructure(ps1)
+   ps2 = _restruct(θ)
+   ps3 = deepcopy(ps) 
+   ps3.WB[:] = ps2.WB
+   ps3.Wpair[:] = ps2.Wpair
+   return set_parameters!(V, ps3)
+end
+
 # --------------------------------------------------------------- 
 #   AtomsCalculatorsUtilities / SitePotential based implementation 
 #