Keep in mind that the 70 FPS notation from vanilla JJ2 is apparently fake. The actual FPS on newer systems is normally a lot higher.

JJ2 does some minor stuttering for me as well.

That said, I don't think there's currently a way to force the FPS to cap at a specific value. It appeared to cap at the monitor refresh rate on CRT displays, giving that smooth stutterless animation, but it doesn't do that on my current LCD display (not even on Windows 98 and XP).

Maybe a JJ2 FPS limiter could be a good Plus suggestion?