I use a 75/4 Ektar for 6X7 on a beseler 23C. I was pleasantly surprised that it covered. I was using a 105 for 6X7 and 6X9. I still use the 105 for 6X9, but I now use the ektar exclusively for 6X7. I can't tell the difference between the ektar and a 105 componon. Maybe I just got lucky and got a good one. I usually expose at f11 - f8.
They come up every so often on ebay, and they are pretty cheap. I think I paid about $15 for mine.
I was using a 75/4.5 componar for 6X6 and it just didn't have the sharpness I wanted, so I thought I'd try the Ektar before spending lots more on a componon/nikkor/rodagon.
IMHO, ektar lenses are the most underrated lenses out there, both for med and lrg format cameras and enlarging lenses. The commercial ektars still bring top dollar on the used market.
I use my 127/4.7 ektar from my 4X5 on my 2X3 Century graphic. The sharpness is right up there with the 80/2.8 Xenotar and 105/3.5 Colour Heliar I usually use on the Century. The four element Ektar doesn't give anything up to those five element lenses.