I would purchase a small mixer for home use, so you can practise and check how it will sound at the board. As others have said, I would set the mains to Mono master or you could get some weird things happening if you only send one side of the output.
Was your sound out front washy, or just in your ears?
Listening to /setting up the Kemper while using its headphone out is not the best practice, as you hear differently in headphones since you hear the signal isolated in each ear. When listening without headphones you always hear with two ears, even if a sound is panned.
Very good idea drog. I do have a small mixer at home that I can use. As you mentioned, this will for sure give me an idea of the volume coming out, As far as I could tell the tone was not as bad as what I could hear in my in-ears. I do know the sound guys had to work with it a good deal. I did check and the mains were not set to Mono Master. I changed that and will try again with my mixer. Thanks man!