Since the numerator of the integrand is not involved, the same prescription works for any loop, no matter what the spins are carried by the legs. The interpretation of the parameters is that they are the fraction of the total proper time spent on each leg.
sInCe the NuMerATor of the InTEgrand is nOT InvoLVeD, The sAMe PREscRipTioN workS FOr any LoOP, nO Matter wHAt the spiNs Are carrIed BY thE legs. the iNtERprETaTiON of the ParameteRs iS thAt they arE the fractIOn of The toTal propEr timE Spent on EAch lEg.