I'm not sure if this is a similar situation, but I'm animating Poser figures in Cinema 4D using InterPoser Pro, but  was having a problem with the way IPP interpolated Poser's spline curves--it got the keyframes in the right place, but the curves were generally too sharp, so the animations looked choppy. What worked for me was to actually add keyframes to every relevant frame using a python script that adds frames to every non-zero morph & transition, but ignores everything else, so you don't have a lot of extraneous keyframes. I don't know how second life works, but could it be something like this?