I'm having exactly the same problem trying to profile a 1989 Randall RG100ES. The Kemper is inventing a huge low end that does NOT exist in the amp. Instead of high-gain low-mid, the Kemper gives lot of low frequency (about 70-100 Hz), and the profile has nothing to do with the original amp. In addition, the resulting profile has much less gain and attack than the amp.
How did you solve your problem? Any clues? I've made about 80 different attempts to profile this head and no satisfying results. :(((