Here is the top portion of make_sumfiles.txt with the camera model for the Cassini ISS. "608 IAPETUS" and "IAU_IAPETUS BFRAME" will need to be changed appropriately.
2 NCAM 'CASSINI_ISS_NAC' 1024 1024 NPXA, NLNA 2002.703 512.5 512.5 MMFLA, PX0A, LN0A 83.3333, 0, 0, 0, 83.3428, 0 KMATA 0, 8.28E-06, 5.45E-06, -19.67E-06 DA 160, 4095 T1,T2 'CASSINI_ISS_WAC' 1024 1024 NPXB, NLNB 200.7761 512.5 512.5 MMFLB, PX0B, LN0B 83.3333, 0, 0, 0, 83.3411, 0 KMATB 0, 60.88E-06, 5.28E-06, -71.86E-06 DB 160, 4095 T1,T2 1 NSC -82 CASSINI 1.d-1,1.d-1,1.d-1 sigV0 3.d-4,3.d-4,3.d-4 sigPT 608 IAPETUS 'IAU_IAPETUS' BFRAME 'LT+S' ABCORR KERNELS ../CASSINI/DATA/naif0012.tls ../CASSINI/DATA/cas_iss_v10.ti ../CASSINI/DATA/cas_v40.tf ../CASSINI/DATA/cas_v42.tf ../CASSINI/DATA/cpck31Oct2017.tpc ../CASSINI/DATA/cas00172.tsc ../CASSINI/DATA/de421.bsp ../CASSINI/DATA/sat286.bsp ../CASSINI/DATA/051212AP_RE_90165_14363.bsp ../CASSINI/DATA/041014R_SCPSE_01066_04199.bsp ../CASSINI/DATA/041219R_SCPSE_04199_04247.bsp <snip>
Example INIT_LITHOS.TXT is here INIT_LITHOS.TXT.