I had a Janome 1600 P QC(similar to your Juki) on a Little Gracie II and it worked well. I did purchase the Grace stitch regulator too and it made things so much easier.
I have another set up now on another Grace company frame and cannot say enough about the quality of their frames!
Also the quality of their customer service! (the original stitch regulator just wouldn't run and they tried to problem solve it over the phone with me, then sent me an entire new one)