I've been playing bass since '87 or so and started on four string. I believe I purchased my first fiver in '01 or maybe '02. Since then I've played fives a lot, maybe 85% of the time. But still to this day, it seems like my brain is still wired for four strings. When playing or sight reading on a five, it's smooth and fluid, but it just feels like there is some extra processing going on in my head, similar to the delay from a digital wireless unit. You can't perceive or measure the delay in the A/D D/A conversion, but you know there is something additional happening. I pulled out the four string tonight, first time in a long time and ran through some songs and the playing was fluid and effortless. So, I guess what I'm getting at is that many times we put a four string in the beginner's hands. That's fine if you want to play a four string, but if you think you want to play five or even six, just suck it up and start on that. Wire your brain the right way to start. All IMHO.