Hi Bill,
Have you check page 65 of the owners manual ?
I think you might find this is what your looking for.
I`m don`t have one yet , I`m still looking , but I have read the manual , and if I`m correct you can spilt the KB in many ways or just have the "lower" and "upper" where ever you want it.
If had actually had the E80 , I could be of more help.
But I`m sure there must be a way to get a spilt point anywhere you want , and then layer you voices.
Manual bass / lower 1 & 2 + upper 1 /2 /3 , if you can`t do that , then something is very strange.
Every arranger that I have played as well , gave you the option of a set spilt.
Please post if this helps , thanks.
Good luck , and take care.
Gary