RE: Newbie to IMAC
I tend to believe you are right regarding the desirability of larger fuse/span ratios. I'm not sure I have the talent or experience with a variety of airframes to conclude this personally, but I base it off of the current "pro" kit planes that are popular as well as pattern plane design.
However, don't get hung up on it or an Extra xxx vs and Extra yyy. Practice with nearly any of the modern airframes will yield better results.
You might want to look at 80cc designs. They seem to be a good compromise point in size, cost, and performance.