Darren,
I am glad you're leaning towards flat EQ and on board recordings (where possible). That should be a good reference point. At least she was even kind enough to do 'something' when I told her of what we were doing here and your requirements - after not seeing any Tyros 4 postings.
Scott - you're right. I did mine flat just to have a base as everyone's EQ setting would be different (depending on internal speakers, what PA they use ... etc). Using a flat setting should be a good foundation for all to follow - but yet again, not everyone's keyboard will sound great with a flat EQ setting.