Do they make a fully adjustable extension tube for m4/3? I just bought a Jupiter 9 lens from here, and with the current setup of going from the Zenit 39 with a M42 ring adaptor to the M42 to m4/3 adaptor, I loose infinity focusing (which isn't the purpose of the lens, but it would be nice to have). I bought a m39 to M4/3 adaptor, and the thing is much shorter than the m42 to m4/3, so it but puts the lens too close to the sensor. If I had something adjustable, I could probably get spot on with it..that and then it would allow me to keep my m42 adaptor on my pentax lens. I'm not sure how to calculate the exact distance needed, which is why I thought fully adjustable would be better.