Over the years of trying different lengths and styles of Toelke longbows, I have settled on 64" as my optimum length at my draw of 29.5". Having said that, I went with the 66" Super D. Didn't shoot a 64", which I am sure would have been fine, but bonded with the 66". On the ASL's I've tried, getting the last little bit of draw became frustrating. To complicate things, I had to mentally recalibrate every time I wanted to shoot my D-R bows. Just couldn't go back and forth.
Not so with the Super D. Just seems smoother to get the last bit of draw and can easily interchange with my other bows.
Going with the 66", I felt gave me a better chance to regain some of the draw normally lost (1/2") shooting this style of bow. Not sure a 68" would be any added benefit.
Take what I think with a grain of salt, the wife does. Mike