I tried the a contraption that screws on the lens. It works, kinda but prevents one from seeing apertures. Basically to unelegant to even what to use. Would rather hold the filter in place with my hand.
I bought a Valoy a year ago and just started using it. Do you need the DOORX extention tube? My El Nikkor f/2.8 and Focotar work fine without a DOORX.