I scan MF with a V700 and a betterscanning holder. IMO the betterscanning holder is worth the money. It's not just the holder, but a procedure to follow to ensure proper focus and optimum resolution. I think I can produce files from 645 plenty good enough for a 16x20 print.
Very interesting comment MDR. The bit about the V750 does worry me slightly though. Are you saying that having gone to all the trouble of capturing an analogue file, I am going to be dissapointed with the results. I have read that people do use the better scanning holder but I do not like the idea of dropping another £100 on a holder.
I bought two pieces of "anti-glare" glass that just fit in the width of the betterscanning grooves; a loose fit lengthwise. That is the ordinary anti-glare glass, not the pricey "museum" vacuum-coated glass. This is effectively anti-Newton glass. Betterscanning also sells AN glass, your decision.
I tape the negative with the non-emulsion side against the underside of the glass, taping only the ends over the gaps. It helps if the camera exposes with wide gaps. Then lay the glass in the betterscanning holder. Taping + lateral ridges of holder + film natural curl result in film flat against glass plane.
I found the optimum height of the adjustment screws by repeatedly scanning and saving in jpeg the same portion of an image with fine detail, and maximizing the size of the jpeg file.
I apply an unsharp mask filter, with radius 1 and 100%. Sounds simple-minded, but actually the result of a systematic approach based on FTM; too long to explain here.
I can send you a sample file if you'll PM me and provide your email.