This is a Baan IVc4 answer, but it may still apply to Baan 5c
It is not possible to use the product configurator session (tipcf5120s000) with AFS.
The way we do it is to insert a variant into the product variant tables tipcf500, tipcf510 & tipcf520 - make sure the validity flag on the variant (tipcf500.vali) is set to "No". Use the session tipcf5200m000 to ensure the variant validates correctly. Then using the AFS functions to set the default answer (forgot the exact function now), you can say "No" to the question "Configure product variant now?", and enter the variant number that you have just created above. Then create the product variant structure as normal with tipcf5260s000.