Coping saw - video

Very nicely executed. I made a very similar one with a frame section of 12x6mm but found it heavy and tiring.
I prefer the very light coping saws from my childhood. You get a better feedback / feeling of the cutting (resp. jamming) forces.
If you need stiffer frames, you can shorten the 'U'. If you want to accomodate a 170mm blade, you open the 'U'.
To avoid the fumbling with different blades I keep 5 coping saws ready, 3 different frames, different blades.