The drive to do something different came from my desire to keep cello building fresh and my instructor's suggestion to make something comfortable. Like a lot of people, my instructor is smaller than average and standard sized cellos can be uncomfortable for non standard sized people. I find my cellos to be comfortable while playing them, but when I stand up after an hour of play, my legs feel pretty stiff. I suspect this situation will intensify with age.
My experience from making different sized violins is that great sounding instruments can come in different shapes and sizes, and since great sounding vintage cellos have mostly been reduced from their original size, perhaps a smaller cello can be comfortable, easy to play and sound great. BTW, I've come to realize that string choice is not only time consuming, but very effective in bringing out the best in a cello. So, maybe the right strings will compensate for size.
I've gathered input from a variety of players, analyzed measurements from a dozen cellos and played a few cellos of different shapes and sizes. I've ended up taking inspiration from the "Simpson" Guagagnini . Compared to my current model, it's a little shorter, narrower in the upper and lower bouts, and a little bit wider in the C bout. I hope to keep the string length at what's considered to be normal for a full size violin.
Already I'm eager to hear how it sounds, but I'll likely have to wait until about a year from now as I hope to have it ready for the start of the outdoor varnish season next May.